I think this is a recipe for disaster. As much as I'd like to believe that we're among a group of mature people who can express their views rationally and appropriately, I'm afraid a OMS policy would lead to people getting in "one last dig" and creating a moderation nightmare.

Moderators fire a warning shot when topics get out of hand. It is NOT an invitation to post one final thought about the deviation, it is a clear signal that says "get back on topic or this thread will be closed".