It doesn't need to. It's banning any nick having your same host mask - that isn't you. The "!" prefix prevents it from matching your own join, though since you join without OP you couldn't ban yourself. The @ prefix would probably be better since you could only be OP if the join weren't yourself.
This code would also ban a 2nd nick joining from your own PC.
My point exactly.. he doesn't want people banned that match both his ident/nickname string even if they are on his same ip. He only wants people that log on using his ip but don't share his ident and also share a string that will be common in all his nicknames. You are assuming he only wants a single client matching his IP in the channel, when I believe he only wants unauthorized users on his IP to be banned.
