When you kick some ass, you always take harm on a hit (7+).
This seem appropriate, I guess, unless I'm playing Buffy or some other actual ass-kicker. Sure, invincible helps a lot, but I think it's a bit weird that the most-ass-kicking characters will be taking the most harm. As written, the move should maybe be called "when you get in a fight."
FWIW, Dungeon World's fighting move originally worked like this one (trade harm on any hit) but it turned out to be way too much harm coming back on the PCs, so it was revised.
I haven't played MotW yet, though, so maybe I'm way off. Anyone seen this in play?