Well for one, it's not a reliable way of doing it
What if they change their nick 5 seconds after joining the room? They get banned for it.
how about this:
ON *:JOIN:#:$+(.timer,$mask($fulladdress,0)) 1 10 jpqbanner $fulladdress #
alias jpqbanner if ( !$ialchan($mask($1,0),$2,0) ) { ban -u90 $mask($1,2) }
I haven't tested that out, but it should work. If they join and change nicks, it'll leave them alone. It'll also do a smarter ban because the one you set up, if someone came on with *!*@*.ipt.aol.com, then everyone in the room using aol would end up getting banned too.