With regard to the email validation thing. An email is sent to dingdong@spuddy.idiot.com. idiot must click to a confirmation screen, with the ip shown(no proxy's allowed). If they still continue on their merry way, you firewall the ip.
Using regex, only allow so many occurrences of a given alias. I know that they use some type of db here, ive seen error messages with the sql in it. Triggers with sql that issue notifications or blocks when a regex of a known alias appears, but is NOT that alias(extra letter, what ever). Admin comes in and eats the person alive.
The one thing I'm not real thrilled about with TR, you can change your alias. Well, stop that. Pick your alias, and go with it.
I am a errr, what ever tech on an irc network. We have fought the battle of spam bots and stuff. regex, enforce validation. Your people will moan and groan a bit, but when they recognize it is for their protection. They understand and go with it.
Also, every posting board that I have ever admined. I see the ip of the poster because I am the admin. Bloody block that ip completely. That falls under, go away twit. leave us alone.
With regard to stopping proxy's. There is various list's out there with known open proxy's. Unfortunately, there is always new ones. Spoofing ip's has become such an art form, but most case's simple protections will stop the script kiddies. And I would guesstimate that this person is nothing but a script kiddy. If it is found that this person keeps coming back, under the same ip and pretending to be tigger. This is a case of stalking, miss representation. Contact the isp(doesn't usually do squat, but you never know).
Dan