Frankly I find the idea of hellbanning childish, but it has a long history on the internet.
But if you hellban them, then they'll log in just fine, they'll post just fine... but no one will respond to their posts. Eventually they'll get bored because they can't get a rise out of anyone and they'll leave.
That's not too surprising, since the name (though possibly not the practice?) originated at SomethingAwful, and SA bans are pretty deliberately intended to be a mixture of serious and prankish, with a bit of arbitrariness thrown in.
This isn't the whole picture. He's, unfortunately, schizophrenic. Read [http://news.ycombinator.com/item?id=3642308] and [http://qaa.ath.cx/LoseThos.html].
[1]:http://news.ycombinator.com/threads?id=losethosHe dropped a hard J, so we ghosted him on the spot.