We're unable to delete accounts due to a few reasons.
1. Security - you may have previously or even recently done/concluded sales transactions in the forum. Should a dispute arise, it would be hard to track back your postings on the forum.
2. Continuity - Should your account be deleted, posts that you have made in the forum will be marked as posted by anonymous. Your contributions to the forum - however small they might have been are important to the community.
Due to the above mentioned reasons, we do not delete accounts. If you're no longer using it, just don't login to it anymore.