I spam thumbsup, mastery 7, and bm whenever I can. And as a 1,2 million mastery points Yasuo I can tell you why we are like this. Due to all the hate towards Yasuo players, we constantly get shit from everyone that doesn't play him. So whenever we do good or pull off a play, we bm or show off our "mastery 7 / thumbsup" thing. You see, we feel that we actually did something good, and that we get some kind of revenge for all the hate towards him. If someone on the enemy team calls me out for being bad for just playing a certain champion, I will even bm harder if I'm close to that person ingame.
I'm not toxic at all though when it comes to flaming in chat etc, I just love to bm or show off mastery level 7.