Quite often I have seen questions here on q2a, such as where is delete? help. Users just do not find the delete button, because it is not showing up. Just after pressing "Hide" it will appear - but not always* either.
Improving usability: To make it clear to users I would just change the tooltip for the Hide button from "Hide" to "Hide - then you can also delete".
PS: *The delete button only appears if there are no dependencies. In other words, if there are comments that have the post as parent, the post cannot be deleted. Maybe this should be pointed out with a notice as well.