Why post_number?

Development
8

That makes sense, but why is reply_to_post_number used to identify which post a post is a reply to? If post_number only exists to make URL’s look prettier, why is it the identifier that replies depend on? Wouldn’t it be more consistent to make replies depend on post_id, a much more fundamental identifier? You would have to check that a post with that post_id existed in the thread the reply was being posted in, but you already have to do that with post_number.