I rarely play strangers but in 2017 I'm going to start - regardless, I think an opponent resigning in a 2p game is slightly rude when it's done on my turn. When I resign I almost always wait for my turn in order to end it - it just feels crappy to be rolling on a turn and then have the game seize up and I wonder, 'did the server die, is my Internet connection out, etc.' only to find out my opponent resigned. But yeah, in 2p games I can't see who has a problem with resigning except maybe players that haven't played many games and want to see how an X/Y/Z engine plays out.