I just got done playing a rank up battle where the opponent rage quit (of course) after I had once.
Now I coulda swore that before, when someone had rage quit on me during my rank up, that it did not give me credit. But this time when I got into another ranked match I had notice that my win streak went up by one and I had ranked up.
So, has it been this way for a while or if not, maybe this is from that recent patch?