every poster can edit or delete his own post content and subsequently the Staff would delete every empty posts.
Members have report button for that too.
What if a poster would delete the starting post of a thread? The whole thread would be deleted. Not good for other posters.
I think some moderation tools have to be restricted to the forum's Staff members only, because they are experienced in these stuffs and can delete and in case merge or move posts without causing damages and additionally can edit posts numbers references or links contained in a thread when a post is erased.
Staff deletes only nonsense and pure thanking posts, all other obsolete posts go to trash and are not deleted.