I've not seen that one either Clinton although I did find something similar when I looked at phpbb yesterday. That one allows the admins to decide whether deletions are allowed as well as edits. The built in rule for a deletion by a user is just that - it is dissallowed if the post has been replied to.

I've not looked at which way they implement it. Probably they take advantage of a post having a sequentially allocated unique ID or use the date/time stamp, either of wich could work but when thinking about that approach, it did lead me to wonder what you do in this scenario...

Lets say a post was replied to and that reply was then deleted (and there are no other replies). Would you say that the earlier post no longer classes as being replied to as the reply no longer exists or would you take the historical view and say it was once replied to?