Question mark? ????

I’ve been noticing this player during my *Monster Hunter Wilds* quests; I play with a friend, and we’re sort of "beginners." We recently reached the endgame content and are only just now exploring high-level quests—actually, we’re farming Gogmazios. This random player’s name is literally just a question mark, and his auto-chat messages are just a bunch of "? ? ? ? ?". This is the second time I’ve run into him: he joins, helps out, plays well, and then vanishes. I’ve heard rumors about him. Even within our own group. What’s the theory behind this conspiracy? I’m really curious, haha.