How do I proceed?
The Help Page is a generic page for SMF.
You cannot delete your account. Admins can delete your account, but they won't.
Judging by other threads here, and looking at the help section, it should be technically possible. Heck over at Litecointalk you can do it yourself, and it looks like the same forum software.
1) Make sure that the account wasn't hacked.
2) Check for any existing scam accusations against the person.
3) Check their outbound PMs for scammy behavior.
This is a long, painful process, so theymos just doesn't do it anymore.