Alright so deleting posts has a recent board: Ability to delete your own posts which has a staff response.

The comment deleting part is new otherwise I would lock this board up as being a duplicate of the board mentioned. On the same grounds as the forum post deletes I highly doubt this would happen. Only staff can remove a post.

Yeah I would not be in favor of deleting old forums. That is why when we can we lock them up. S&I's rule sticky is form 2010 but gets updated. Your way would have it deleted. There are also many guides .etc that are updated despite having an old timestamp.