Just make your password 256 characters long, delete all your posts, change your email to a five minute disposable email, then lose the password. You cannot enter your account, you cannot recover the password, and you have no posts, nor evidence that you were ever here.
You can't get better than that

I don't see what the big deal is, if you don't log in ever again eventually the account dies anyway,
assuming the admin doesn't prune off all the old growth after a period of inactivity
If there's posts that are causing grief, the poster should just delete them
You sign up to a forum, you agree to the fair use terms and conditions, you get accepted, it's FREE, no one is key logging you,
what's the problem?
It's an electronics forum not a nutjob troll infested politics, religion, or UFO spotters hangout.
Please Consider