I can't abide by any quitting. Lag is going to happen and ranking means nothing. To me, the only difference between the game modes is 'Simple' means 'random-picking, button-mashing silliness', 'Ranked' means 'might try an actual combo now and then' and 'Lobby' means 'chilling with friends, we might bother to have a fight at some point if we fell like it'.
If I'm in ranked and someone comes up that I have a poor connection with or it's obvious that they're playing in a boring fashion or one of us is clearly infinitely better than the other, I'll just sit it out. Considering how long it an takes to get out of and then into a new match it's really no quicker to quit than it is to eat a couple of rounds, and sometimes lag sorts itself out after 10-15 seconds.