I'm fairly certain that a poster can delete their own posts. And if they started the thread, doesn't that delete the whole thread?
I think it's a separate thing, but yes, original posters can delete threads that they started.
I know we were talking about the possibility of disabling that, though, due to its having been used in just this sort of manner (deleting an entire thread in a fit of pique when the OP didn't get the validation they wanted, or whatever). Tom, did you determine whether it's possible to remove that permission from the thread starter?