Say I picked a really bad UserName for the forum (as above). There’s no way to change it without destroying the account, right? And how do I destroy my own account?
Koz
You could ask an Administrator or Moderator to deactivate your account. I think that would leave your posts intact, though I’m not 100% sure about that. I think you could then sign up for a new account using the same (or different) e-mail address. Buanzo should be able to give you a definitive answer on that one.
[Edit] Having just read another post I think that you may be asking how to remove a members name from the forum. As far as I know, this can only be done by removing their posts and deactivating their account. You can do that from the Moderators control panel. PM me if you need more information.
From looking at the Moderator Control Panel it looks as though one of the things that a mod can change is the username. I do note from this guy’s account details though that his registered email address is not the same as his username 
WC
Looks like you are right WC. I wonder if that will update the name on all of their posts - probably will.