Not tell HR and done. Tell HR so they can ensure you are never in a place where you can influence her business success. It happens all the time and the rules about what companies do are very complex. As CEO I doubt he can every avoid the conflict of interests that HR is concerned about in these cases and in turn he can't be both CEO and have these affairs. (but the nurse or waitress down the street would be okay, even the CEO down the street so long as they are not competitors and careful to avoid any interaction with each others as customer/supplier - this is often possible since the CEO doesn't decide which widget to buy)

Hi. I was musing, not pro / con. I mentioned the power imbalance, and I am shrugging at his "wisdom" given his status, but hear me out, it's that everyone seems to have know and kept the fact as an ace in their sleeves. I am sure he didn't fly himself and his mistresses commercially, there is a crew, and gossip spreads. The truth is elsewhere, regardless of each's view on infidelity. I give you Gates, Bezos. Cheers.