Jazz, the description of the informal nights does not match the reality of any of the SS cruises I’ve been on. Over the last 10 years male pax on informal nights are increasingly not conforming to the jacket requirement. I also see fewer dresses on informal nights. But is a jacket that hard to swing? If you have one fairly dark one you should be able to manage it for formal and informal nights.
Also, I didn’t know SS had an evening buffet. Is that something new? If you mean La Terrazza then there is only a buffet for breakfast and lunch, not dinner. It’s table service for dinner, unless that has changed.