I can post the old css file from the forum here in the css section another day
That old Forum also had a Flags feature
When you would hit Reply, it had a Flags option
One could Flag (notify) other users of a post or reply
The Flag (notification) would show up in the users Self Search
I do not remember the limit of how many users one could Flag (notify)
But one could Flag up to the limit, and than hit Reply again just to Flag more users
Too many Flags can overload the database
So to do that today, one would have to put a limit on the Flags per each post
Maybe like 3 or 5