We're all United aren't we?
Join Date: Mar 2013
Re: The re-joiner guy.
^^^ Perma banning someone doesn't ban the IP, just that individual account so they're obviously still free to sign up again with a different email. You can do IP bans but there's like a thousand ways for the person who's been banned to easily get around them plus you also run the risk of accidentally stopping perfectly legitimate users accessing the site, so generally speaking they're not really an advisable thing to do.
tbh there's nothing you can really do other than keep banning him and just hope the guy gets bored of making new accounts.