Why can't I delete posts?

I have some posts that I want to delete for privacy/identification reasons. I click the delete button and it turns red but nothing happens.

Red means that you can see it, but others can’t.
The site doesn’t really delete posts,.it just hides them.
If you log out, you’ll be unable to see that post.
You can also edit/delete the actual content within the deleted post. I believe that will delete it permanently.

This matches with what moderators generally see with a “deleted” post.

Chances are that if you leave the thread and re-enter it, you might just see “hidden post” in the spot where you deleted the post.