You can’t delete your account yourself except an admin decides to do it for you.
But since you have just a few posts on your account, you can just delete those posts or edit them to “delete” after that change your email address to a random email that does not exist and do the same thing to your password by just inputting random password without saving it, that way you won’t be able to access your account again and that should serve the same function as “deleting the account” since you don’t want to access the forum/account again.
Seems not a bad idea, but the deleting of posts is probably unnecessary as scrapers will simply make it easier to access them. If OP creates a throwaway email and password which he can’t remember, he should also create a thread on the reputation board with the idea that he wouldn’t be using the account again and possible many members will tag it, just in case someone else gets access to it they won’t be able to use it for any transaction on the forum again because of the tag should the Mods fail to delete it. This will be similar to how people that do not wish to take loan on the Forum have done. This prevents a scammer using it in future.
A Bitcointalk member only can delete posts but can not delete a thread, opening post of a thread. Even posts if deleted by OP will still be stored by some scrapers.
He can actually delete a thread created by himself but like you said the Scrapers we have can simply make one have access to almost everything posted on the account even after they got deleted.