Or how can I just delete my account?

If the post was made within the last 24 hours, you can edit the post and simply delete all the words leaving an empty post. There may be other ways, but I don't know of them. I am not sure that deleting your userid, however that's done, would remove your posts.

You could try reporting your post and say that you'd like the thread deleted, although I'm not sure if it will actually get taken off or not...

I would like to know this, because I recently found my post was a top search on google. And am horrified that someone I know could recognise me.

I desperately want one of my threads deleted. I don't know why the option isn't already there. I might refrain from posting in future.

The bad news is you can't delete a post. The good news is, well, there is no good news. You should be aware that this is a common thing on the internet. A site may allow you to delete your posts but that usually just keeps it from being displayed. It is never totally deleted. Somewhere it will continue to exist and come back to haunt you in the future. Best to keep that in mind when you write a post. Also, imagine your friends reading it as you write it. Keeps you careful what you say.