Sometimes a ban just isn't enough. Users, after being banned, are still able to edit/change their signature and profile. On more than one occasion now I've had banned users resorting to filling their signature with profanity and changing their avatar to some offensive imagery.
Is there any way to ban a user such that they aren't able to modify such details, especially those that can have an immediate effect on the forum?
Before anyone suggests an IP ban, this particular user has gone through at least 20 IPs in the past month. I don't want to go there.
My final resort is to delete this user, but leave his posts intact as an anonymous username as kind of a deterrant/warning. But doing this means he can register again with the same email address (and the cycle continues). One could argue that he could create an alternate email address anyway, but that would require some effort on his part and I'm counting on him being lazier than me

So before I delete this user I would like to know if there's a way to prevent a banned user from modifying their profile?
Any other suggestions on how to deal with troublesome users are more than welcomed.