say, "Thanks!"? Or respond with a thumb's up, in return? Apparently something happens around 60% -- data is only from my personal experience, but it seems a real effect.
I'm not one of those who gushes MH 'effective/team player' in every game, or starts a wall of chat like some lonely shut-in, but a subset of players seems unwilling to initiate, return, or acknowledge a complement, or briefest of "good game!" comments. Weird.