Post editing problem

To clarify, post editing works fine, but here is the problem.

If I post something, and a day later think of something that needs to be added, the rules require that if there has been no intervening post, I can't post again, but must modify the original post.  If  I disobey, Khassy beats the <fill in blank> out of me.   The problem is that SMF has no provision for flagging the thread as having new material added, based on post modification.  That means anyone following the thread never finds out there is something added.

  Well, if I wasn't older than dinosaur poop, I might have thought of that.

Thanks.