I'm not sure, so don't take this as Gospel, but please check.
I believe an original poster of a comment can delete his own comment; a moderator doesn't have to do that (I'm a moderator, but as your comment was posted in a forum I'm restricted from moderating, I can't do it myself).
But I believe one can delete his own posts.
Open that thread and look at your comment, at the upper-right hand corner, and there might be a "delete" or "remove" button (but on your comments only; it won't appear on others' comments).
Don't take this as Gospel, but give it a look-see.