Sorry to hear you want to delete your forum account.
The forum software we’re running (Discourse) makes it so it’s only possible to delete accounts only if it is relatively new with few posts and afterward they need to request forum admins to delete it (which in this case is anonymization in order to keep post history but remove all personal information related to the account, including account name, email, etc.)
If you wish to have your account anonymized, please message the moderators: request account deletion.
This creates a message where the “account deletion policy” link is currently broken. There is a policy post here, which contains an extended discussion by the moderators on how to handle deletion requests.