Good rule.

I bit worried that it can open the door to punishing someone for just being human and correcting someone's misstep even if it is off topic.

Another problem I can see is moderators being too subjective in what is thought of as "off topic".

Things could be taken too far end evolve into someone taking action against someone because of personal preference. But I will have faith that this will not happen.

There is an obvious joke I could make here about worrying what I just said now was off topic, but I won't tell it.