@Sam2 -I was not disagreeing with the fact that according to the Mishnah Berurah one should wear a hat. I was merely taking issue with Abe Cohen’s first post on this thread namely that, “The Mishna Berura says you ‘can’t’ daven or bentch without a hat.”
You CAN’T shuckle lulav without a lulav, but you actually CAN daven or bentch without a hat. Should you? Ahhh… That’s a different question entirely! According to the Mishnah Berurah you should don an additional head covering for davening and bentching.