system
A chat on subreddit /r/NoStupidQuestions
human
There's 3 criteria we can ask ourselves in these situations. 1. Does anything need to be said at all? 2. Does it need to be said right now? 3. Does it need to be said by me? It looks like he's going to find out. Saying it right now will not change anything. And it isn't your place to tell him, it's hers.

Edit: wow. I didn't expect this to blow up. Thanks for the awards everyone.
gpt
I loved Craig Ferguson’s show and I think about this advice a lot (although you reversed 2 and 3, iirc).

I also think about the fact that he gave this advice in the context of marriage and then got divorced, though.