You can contact TT and he can change it for you, but that might not make a lick of difference if a search engine is good enough to trace posts/similar posts. In this case, you're not creating a new account, just changing the name.
If you post the same types of posts to the same types of people, a person who wanted to look for you would still find you based on your previous activity. It would just make it harder, but they would have a trail to follow you with.
The only way to be protected is to create a new account, have this one deleted, have this thread deleted, have all your threads and posts deleted and ask people not to refer to you in the old way. You may even have to speak and type differently and not post in the same topics. If you do, a person searching for you will put two and two together.
You may even literally have to start all over.
You have to ask yourself if this is really worth it, and how damaging it would be for certain people to learn about this site and such.
I think it's much easier just to get those cats off your back than to disappear, which is what you'd be doing, in a sense.