diff --git a/irc/channel.go b/irc/channel.go
index bcf56cd4..5072c40b 100644
--- a/irc/channel.go
+++ b/irc/channel.go
@@ -84,6 +84,14 @@ func (channel *Channel) receiveCommands(commands <-chan ChannelCommand) {
 	}
 }
 
+func IsPrivMsg(reply Reply) bool {
+	strReply, ok := reply.(*StringReply)
+	if !ok {
+		return false
+	}
+	return strReply.code == "PRIVMSG"
+}
+
 func (channel *Channel) receiveReplies(replies <-chan Reply) {
 	for reply := range replies {
 		if channel.destroyed {
@@ -98,9 +106,10 @@ func (channel *Channel) receiveReplies(replies <-chan Reply) {
 		}
 		channel.mutex.Lock()
 		for client := range channel.members {
-			if reply.Source() != Identifier(client) {
-				client.Reply(reply)
+			if IsPrivMsg(reply) && (reply.Source() == Identifier(client)) {
+				continue
 			}
+			client.Reply(reply)
 		}
 		channel.mutex.Unlock()
 	}
@@ -187,9 +196,7 @@ func (channel *Channel) Join(client *Client) {
 	channel.mutex.Unlock()
 
 	client.channels.Add(channel)
-	reply := RplJoin(client, channel)
-	client.Reply(reply)
-	channel.Reply(reply)
+	channel.Reply(RplJoin(client, channel))
 	channel.GetTopic(client)
 	channel.GetUsers(client)
 }
@@ -216,9 +223,7 @@ func (m *PartCommand) HandleChannel(channel *Channel) {
 		return
 	}
 
-	reply := RplPart(client, channel, m.Message())
-	client.Reply(reply)
-	channel.Reply(reply)
+	channel.Reply(RplPart(client, channel, m.Message()))
 
 	channel.members.Remove(client)
 	client.channels.Remove(channel)
@@ -245,9 +250,7 @@ func (m *TopicCommand) HandleChannel(channel *Channel) {
 
 		channel.topic = m.topic
 		channel.GetTopic(client)
-		reply := RplTopicMsg(client, channel)
-		client.Reply(reply)
-		channel.Reply(reply)
+		channel.Reply(RplTopicMsg(client, channel))
 		return
 	}
 
@@ -267,10 +270,18 @@ func (m *PrivMsgCommand) HandleChannel(channel *Channel) {
 func (msg *ChannelModeCommand) HandleChannel(channel *Channel) {
 	client := msg.Client()
 
-	for _, modeOp := range msg.modeOps {
-		switch modeOp.mode {
+	if len(msg.changes) == 0 {
+		client.Reply(RplChannelModeIs(channel))
+		return
+	}
+
+	changes := make(ChannelModeChanges, 0)
+
+	for _, change := range msg.changes {
+		switch change.mode {
 		case BanMask:
 			// TODO add/remove
+
 			for _, banMask := range channel.banList {
 				client.Reply(RplBanList(channel, banMask))
 			}
@@ -282,12 +293,14 @@ func (msg *ChannelModeCommand) HandleChannel(channel *Channel) {
 				continue
 			}
 
-			switch modeOp.op {
+			switch change.op {
 			case Add:
-				channel.flags[modeOp.mode] = true
+				channel.flags[change.mode] = true
+				changes = append(changes, change)
 
 			case Remove:
-				delete(channel.flags, modeOp.mode)
+				delete(channel.flags, change.mode)
+				changes = append(changes, change)
 			}
 
 		case Key:
@@ -296,34 +309,33 @@ func (msg *ChannelModeCommand) HandleChannel(channel *Channel) {
 				continue
 			}
 
-			switch modeOp.op {
+			switch change.op {
 			case Add:
-				if modeOp.arg == "" {
+				if change.arg == "" {
 					// TODO err reply
 					continue
 				}
 
-				channel.key = modeOp.arg
+				channel.key = change.arg
+				changes = append(changes, change)
 
 			case Remove:
 				channel.key = ""
+				changes = append(changes, change)
 			}
-		}
 
-		mmode := ChannelMemberMode(modeOp.mode)
-		switch mmode {
 		case ChannelOperator, Voice:
 			if !channel.ClientIsOperator(client) {
 				client.Reply(ErrChanOPrivIsNeeded(channel))
 				continue
 			}
 
-			if modeOp.arg == "" {
+			if change.arg == "" {
 				// TODO err reply
 				continue
 			}
 
-			target := channel.server.clients[modeOp.arg]
+			target := channel.server.clients[change.arg]
 			if target == nil {
 				// TODO err reply
 				continue
@@ -334,16 +346,21 @@ func (msg *ChannelModeCommand) HandleChannel(channel *Channel) {
 				continue
 			}
 
-			switch modeOp.op {
+			switch change.op {
 			case Add:
-				channel.members[target][mmode] = true
+				channel.members[target][change.mode] = true
+				changes = append(changes, change)
+
 			case Remove:
-				channel.members[target][mmode] = false
+				channel.members[target][change.mode] = false
+				changes = append(changes, change)
 			}
 		}
 	}
 
-	client.Reply(RplChannelModeIs(channel))
+	if len(changes) > 0 {
+		channel.Reply(RplChannelMode(client, channel, changes))
+	}
 }
 
 func (m *NoticeCommand) HandleChannel(channel *Channel) {
diff --git a/irc/commands.go b/irc/commands.go
index 546bbdba..480ed04f 100644
--- a/irc/commands.go
+++ b/irc/commands.go
@@ -402,6 +402,26 @@ func (change *ModeChange) String() string {
 	return fmt.Sprintf("%s%s", change.op, change.mode)
 }
 
+type ModeChanges []ModeChange
+
+func (changes ModeChanges) String() string {
+	if len(changes) == 0 {
+		return ""
+	}
+
+	op := changes[0].op
+	str := changes[0].op.String()
+	for _, change := range changes {
+		if change.op == op {
+			str += change.mode.String()
+		} else {
+			op = change.op
+			str += " " + change.op.String()
+		}
+	}
+	return str
+}
+
 type ModeCommand struct {
 	BaseCommand
 	nickname string
@@ -436,27 +456,47 @@ func (cmd *ModeCommand) String() string {
 	return fmt.Sprintf("MODE(nickname=%s, changes=%s)", cmd.nickname, cmd.changes)
 }
 
-type ChannelModeOp struct {
+type ChannelModeChange struct {
 	mode ChannelMode
 	op   ModeOp
 	arg  string
 }
 
-func (op *ChannelModeOp) String() string {
+func (op *ChannelModeChange) String() string {
 	return fmt.Sprintf("{%s %s %s}", op.op, op.mode, op.arg)
 }
 
+type ChannelModeChanges []ChannelModeChange
+
+func (changes ChannelModeChanges) String() string {
+	if len(changes) == 0 {
+		return ""
+	}
+
+	str := "+"
+	if changes[0].op == Remove {
+		str = "-"
+	}
+	for _, change := range changes {
+		str += change.mode.String()
+	}
+	for _, change := range changes {
+		str += " " + change.arg
+	}
+	return str
+}
+
 type ChannelModeCommand struct {
 	BaseCommand
 	channel string
-	modeOps []ChannelModeOp
+	changes ChannelModeChanges
 }
 
 // MODE <channel> *( ( "-" / "+" ) *<modes> *<modeparams> )
 func NewChannelModeCommand(args []string) (editableCommand, error) {
 	cmd := &ChannelModeCommand{
 		channel: args[0],
-		modeOps: make([]ChannelModeOp, 0),
+		changes: make(ChannelModeChanges, 0),
 	}
 	args = args[1:]
 
@@ -472,18 +512,18 @@ func NewChannelModeCommand(args []string) (editableCommand, error) {
 
 		skipArgs := 1
 		for _, mode := range modeArg {
-			modeOp := ChannelModeOp{
+			change := ChannelModeChange{
 				mode: ChannelMode(mode),
 				op:   op,
 			}
-			switch modeOp.mode {
+			switch change.mode {
 			case Key, BanMask, ExceptionMask, InviteMask, UserLimit:
 				if len(args) > skipArgs {
-					modeOp.arg = args[skipArgs]
+					change.arg = args[skipArgs]
 					skipArgs += 1
 				}
 			}
-			cmd.modeOps = append(cmd.modeOps, modeOp)
+			cmd.changes = append(cmd.changes, change)
 		}
 		args = args[skipArgs:]
 	}
@@ -492,7 +532,7 @@ func NewChannelModeCommand(args []string) (editableCommand, error) {
 }
 
 func (msg *ChannelModeCommand) String() string {
-	return fmt.Sprintf("MODE(channel=%s, modeOps=%s)", msg.channel, msg.modeOps)
+	return fmt.Sprintf("MODE(channel=%s, changes=%s)", msg.channel, msg.changes)
 }
 
 func NewModeCommand(args []string) (editableCommand, error) {
diff --git a/irc/constants.go b/irc/constants.go
index 4704baaf..0ef8bd87 100644
--- a/irc/constants.go
+++ b/irc/constants.go
@@ -173,24 +173,23 @@ const (
 	ServerNotice  UserMode = 's'
 	WallOps       UserMode = 'w'
 
-	Anonymous     ChannelMode = 'a' // flag
-	BanMask       ChannelMode = 'b' // arg
-	ExceptionMask ChannelMode = 'e' // arg
-	InviteMask    ChannelMode = 'I' // arg
-	InviteOnly    ChannelMode = 'i' // flag
-	Key           ChannelMode = 'k' // flag arg
-	Moderated     ChannelMode = 'm' // flag
-	NoOutside     ChannelMode = 'n' // flag
-	OpOnlyTopic   ChannelMode = 't' // flag
-	Private       ChannelMode = 'p' // flag
-	Quiet         ChannelMode = 'q' // flag
-	ReOp          ChannelMode = 'r' // flag
-	Secret        ChannelMode = 's' // flag
-	UserLimit     ChannelMode = 'l' // flag arg
-
-	ChannelCreator  ChannelMemberMode = 'O' // flag
-	ChannelOperator ChannelMemberMode = 'o' // arg
-	Voice           ChannelMemberMode = 'v' // arg
+	Anonymous       ChannelMode = 'a' // flag
+	BanMask         ChannelMode = 'b' // arg
+	ChannelCreator  ChannelMode = 'O' // flag
+	ChannelOperator ChannelMode = 'o' // arg
+	ExceptionMask   ChannelMode = 'e' // arg
+	InviteMask      ChannelMode = 'I' // arg
+	InviteOnly      ChannelMode = 'i' // flag
+	Key             ChannelMode = 'k' // flag arg
+	Moderated       ChannelMode = 'm' // flag
+	NoOutside       ChannelMode = 'n' // flag
+	OpOnlyTopic     ChannelMode = 't' // flag
+	Private         ChannelMode = 'p' // flag
+	Quiet           ChannelMode = 'q' // flag
+	ReOp            ChannelMode = 'r' // flag
+	Secret          ChannelMode = 's' // flag
+	UserLimit       ChannelMode = 'l' // flag arg
+	Voice           ChannelMode = 'v' // arg
 )
 
 const (
diff --git a/irc/reply.go b/irc/reply.go
index 7099a819..54d2be27 100644
--- a/irc/reply.go
+++ b/irc/reply.go
@@ -144,11 +144,20 @@ func RplJoin(client *Client, channel *Channel) Reply {
 }
 
 func RplPart(client *Client, channel *Channel, message string) Reply {
-	return NewStringReply(client, "PART", "%s :%s", channel.name, message)
+	return NewStringReply(client, "PART", "%s :%s", channel, message)
+}
+
+func RplMode(client *Client, changes ModeChanges) Reply {
+	return NewStringReply(client, "MODE", "%s :%s", client.Nick(), changes)
+}
+
+func RplChannelMode(client *Client, channel *Channel,
+	changes ChannelModeChanges) Reply {
+	return NewStringReply(client, "MODE", "%s %s", channel, changes)
 }
 
 func RplTopicMsg(source Identifier, channel *Channel) Reply {
-	return NewStringReply(source, "TOPIC", "%s :%s", channel.name, channel.topic)
+	return NewStringReply(source, "TOPIC", "%s :%s", channel, channel.topic)
 }
 
 func RplPing(server *Server, target Identifier) Reply {
@@ -207,9 +216,11 @@ func RplTopic(channel *Channel) Reply {
 		"%s :%s", channel.name, channel.topic)
 }
 
+// <nick> <channel>
+// NB: correction in errata
 func RplInvitingMsg(channel *Channel, invitee *Client) Reply {
 	return NewNumericReply(channel.server, RPL_INVITING,
-		"%s %s", channel.name, invitee.Nick())
+		"%s %s", invitee.Nick(), channel.name)
 }
 
 func RplNamReply(channel *Channel, names []string) *NumericReply {
@@ -238,7 +249,7 @@ func RplEndOfWhois(server *Server) Reply {
 
 func RplChannelModeIs(channel *Channel) Reply {
 	return NewNumericReply(channel.server, RPL_CHANNELMODEIS, "%s %s",
-		channel.name, channel.ModeString())
+		channel, channel.ModeString())
 }
 
 // <channel> <user> <host> <server> <nick> ( "H" / "G" ) ["*"] [ ( "@" / "+" ) ]
diff --git a/irc/server.go b/irc/server.go
index 1f5491c0..6648e129 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -270,7 +270,6 @@ func (m *NickCommand) HandleRegServer(s *Server) {
 
 	client.nick = m.nickname
 	s.clients.Add(client)
-	client.Reply(RplNick(client, m.nickname))
 	s.tryRegister(client)
 }
 
@@ -414,22 +413,31 @@ func (m *PrivMsgCommand) HandleServer(s *Server) {
 func (m *ModeCommand) HandleServer(s *Server) {
 	client := m.Client()
 	target := s.clients[m.nickname]
-	if client == target {
-		for _, change := range m.changes {
-			if change.mode == Invisible {
-				switch change.op {
-				case Add:
-					client.invisible = true
-				case Remove:
-					client.invisible = false
-				}
-			}
-		}
-		client.Reply(RplUModeIs(s, client))
+	// TODO other auth
+	if client != target {
+		client.Reply(ErrUsersDontMatch(s))
 		return
 	}
 
-	client.Reply(ErrUsersDontMatch(s))
+	changes := make(ModeChanges, 0)
+
+	for _, change := range m.changes {
+		if change.mode == Invisible {
+			switch change.op {
+			case Add:
+				client.invisible = true
+				changes = append(changes, change)
+
+			case Remove:
+				client.invisible = false
+				changes = append(changes, change)
+			}
+		}
+	}
+
+	if len(changes) > 0 {
+		client.Reply(RplMode(client, changes))
+	}
 }
 
 func (m *WhoisCommand) HandleServer(server *Server) {
diff --git a/irc/types.go b/irc/types.go
index 487bccab..554f5093 100644
--- a/irc/types.go
+++ b/irc/types.go
@@ -15,6 +15,10 @@ type Mask string
 // add, remove, list modes
 type ModeOp rune
 
+func (op ModeOp) String() string {
+	return string(op)
+}
+
 // user mode flags
 type UserMode rune
 
@@ -37,9 +41,6 @@ func (mode ChannelMode) String() string {
 	return fmt.Sprintf("%c", mode)
 }
 
-// user-channel mode flags
-type ChannelMemberMode rune
-
 type ChannelNameMap map[string]*Channel
 
 func (channels ChannelNameMap) Add(channel *Channel) error {
@@ -84,19 +85,19 @@ func (clients ClientNameMap) Remove(client *Client) error {
 	return nil
 }
 
-type ChannelMemberModeSet map[ChannelMemberMode]bool
+type ChannelModeSet map[ChannelMode]bool
 
-type ClientSet map[*Client]ChannelMemberModeSet
+type ClientSet map[*Client]ChannelModeSet
 
 func (clients ClientSet) Add(client *Client) {
-	clients[client] = make(ChannelMemberModeSet)
+	clients[client] = make(ChannelModeSet)
 }
 
 func (clients ClientSet) Remove(client *Client) {
 	delete(clients, client)
 }
 
-func (clients ClientSet) HasMode(client *Client, mode ChannelMemberMode) bool {
+func (clients ClientSet) HasMode(client *Client, mode ChannelMode) bool {
 	modes, ok := clients[client]
 	if !ok {
 		return false