The nick mangling only happens when the remote user has [] in their nickj and they are connecting to my mIRC on port 59 to establish a CHAT. If I connect to them to establish a CHAT, then the nick does not get mangled. The former case happens when the remote user is behind a firewall or NAT router and has no way of accepting a CHAT connection from me, so they have to initiate a CHAT connection with me.