fix #1178

irc/channel.go

 		chname = fmt.Sprintf("%s%s", modes.ChannelModePrefixes[minPrefixMode], chname)
 	}
 
+	if channel.flags.HasMode(modes.OpModerated) {
+		channel.stateMutex.RLock()
+		cuModes := channel.members[client]
+		channel.stateMutex.RUnlock()
+		if cuModes.HighestChannelUserMode() == modes.Mode(0) {
+			// max(statusmsg_minmode, halfop)
+			if minPrefixMode == modes.Mode(0) || minPrefixMode == modes.Voice {
+				minPrefixMode = modes.Halfop
+			}
+		}
+	}
+
 	// send echo-message
 	rb.addEchoMessage(clientOnlyTags, details.nickMask, details.accountName, command, chname, message)
 
 	for _, member := range channel.Members() {
 		if minPrefixMode != modes.Mode(0) && !channel.ClientIsAtLeast(member, minPrefixMode) {
-			// STATUSMSG
+			// STATUSMSG or OpModerated
 			continue
 		}
 
 		}
 	}
 
-	// #959: don't save STATUSMSG
+	// #959: don't save STATUSMSG (or OpModerated)
 	if minPrefixMode == modes.Mode(0) {
 		channel.AddHistoryItem(history.Item{
 			Type:        histType,

irc/help.go

   +C  |  Clients are blocked from sending CTCP messages in the channel.
   +u  |  Auditorium mode: JOIN, PART, QUIT, NAMES, and WHO are hidden
          hidden from unvoiced clients.
+  +U  |  Op-moderated mode: messages from unprivileged clients are sent
+         only to channel operators.
 
 = Prefixes =
 

irc/modes/modes.go

 	SupportedChannelModes = Modes{
 		BanMask, ChanRoleplaying, ExceptMask, InviteMask, InviteOnly, Key,
 		Moderated, NoOutside, OpOnlyTopic, RegisteredOnly, RegisteredOnlySpeak,
-		Secret, UserLimit, NoCTCP, Auditorium,
+		Secret, UserLimit, NoCTCP, Auditorium, OpModerated,
 	}
 )
 
 	Secret              Mode = 's' // flag
 	UserLimit           Mode = 'l' // flag arg
 	NoCTCP              Mode = 'C' // flag
+	OpModerated         Mode = 'U' // flag
 )
 
 var (