rather than ban and if the alcatraz route hasn't yet worked, i'll also just put them into the "Moron group", where a board hack will choose from an array of pre-defined posts. Regardless of what they type and 'Submit', the addpost/editpost routine will instead pick from (for example)

1. i'm an idiot
2. yeppers, marbles are sharper than i am
3. holy crap, i'm a moron
...

etc..

they can edit or whatever, but still end up with a randomly generated string of idiotic stuff.

when their sockpuppets reappear, they get lumped into that group..

i find that they eventually tire and give up.. all the same time providing entertainment for the onlookers..

2c