If it's the negative rep you're concerned with you can hide it until you have good rep.
(Edit: Oops! You can't. Just found that out. Guess the FAQ needs that bit removed.)
Of course you may have gotten negative rep from posting this thread (which, judging by your previous content is entirely possible).
Still not sure why people request account deletions. When I don't want to go back to a forum I just "don't go back". Of course this is usually due to me losing interest or forgetting that said forum actually exists. I haven't wanted to leave a forum due to a temper tantrum for quite some time now (15+ years?). Actually, even when I did have a temper tantrum I didn't request an account deletion, I just went around and deleted all my posts and threads. Now that's how you leave a forum.