I don't think you can - the best bet is to pm Talkmorgan and request a deletion I guess.
I have never known this to be requested but maybe it has happened before.
Some of the older hands may know how to.
If there is a good reason to delete a post; privledged information that should have been kept confidential, something that could be offensive, etc. Simon will delete the post for you. Just send him a PM with your request and the explanation as to why you want it deleted.