I always try to apologize if the flow of battle permits.
I tend not to apologize when their first reaction is to turn around and whack you. Had Mentok do that to me the other day. Accidently hit him in a fight, go to type sorry and get a steel pick or something in the skull. We (a group of 8) then run into two guys. He gets right up on my ass, and just as the last guy drops he hits me in the back, killing me. Eh, but he's a pretty cool guy, doesn't afraid of revenge tks.