You would need to contact the forums admin about that, but inactivating an account doesn't remove all old posts, as likely most are in threads, and removal would affect the contents of a thread, perhaps making them hopelessly confusing by the loss of continuity in a thread. Why would you want to cause that?

And, because you have posted to other threads, I suppose there is no way to actually remove all trace of "you", if that's what you want.
(There's occasional posts here, when users want to change their account name, and the old posts with the old name continue to exist.)
Of course, if you don't come back, then you are, in effect, gone forever.
Anyway, the most effective way to find out what you can do, if anything, is to contact the forum powers here.
(just curious) I scanned through a bunch of your older posts, etc, and don't see anything outrageous! What do you think happened?
