It appears that the deleted post disappears but the child posts don't. That's fine, but the navigation's broken. I can see your post which is a child of the now deleted one,
http://news.ycombinator.com/item?id=27969 , and if I follow the parent link I get "no such item", fair enough, but the rest of the furniture should still be there so I can go to the delete post's parent. Otherwise, I can't find out what initial thread this was all attached to. Or can only root posts be deleted? If so, that needs to be clearer.
Really, I don't think delete should delete everything. The username, date, and parent at least should still all be present.