Does mIRC supports UHNAMES and NAMESX?
Is it possible to prevent mIRC from sending these PROTOCTL messages? Halting raw event 005 (which instructs the client that the server supports NAMESX/UHNAMES) had no effect.
The answer to that is no. If mIRC connects to a server that uses this feature, it can't be disabled. Halting raw events only stops the script layer from receiving them, this is after mIRC has processed this data internally.