I know I'm sick of the back and forth mod bashing/banning threads... I'm sure others are as well. I believe there is a simpler solution here:
1) Add email verification of all users. Yes, they can always go out and create another Yahoo, Hotmail, or whatever account, but it does take extra time and tends to slow things down enough that trolls move on. Send the email some short period of time -- 15 minutes or something-- after submittal so the person has to wait. Generally people will move on at that point.
2)Have everyone temporarily locked out until they confirm their email address. I'd be happy to verify mine.
3)Go back to the way we were... just let people say/do what they want unless it is just absolutely blatant. Obviously blatant is difficult to define sometimes, but anything using banned foul language repeatedly, posting overtly sexual images, etc., would be blatant. Just being an argumentative troll isn't enough unless it really gets out of hand.
4)Log IP addresses of people's posts within the posts themselves. It would certainly show a trend if a particualr person creates multiple accounts.