Hmmm, that's an empty threat and you know it. I would seek a more reasonable form of dialogue as it's bound to produce more positive results.
I've had a look at that thread and Limited has purposefully added a mod that rewrites e-mail addresses under graphic form, which will stop spammers scanning the forum for addresses to spam publicity at.
When you are banned by the UTAN system, your e-mail is required as contact info. Of course, if this is the e-mail that your ISP provided, perhaps you can supply an alternative e-mail address and ask a board administrator to replace it.
Btw, the forums are there to give you a chance to explain your case. On some occasions, players have been able to lift a ban by promising they won't reiterate whatever behaviour got them banned in the first place. It would seem you partly wasted that chance and that's a shame :/ . UTAN might seem a faceless system but it's actually there to promote some form of dialogue.
And concerning hacks, I'm afraid this invalidates UT2004's EULA :
P.S: The encrypted GUID is a feature of UT2004 implemented by Epic themselves and is sent to the master server each time you play online.