I blame the enemy champion, call it bullshit, blame my jungler, my midlaner, Obama and I let it all out. I hold nothing back and I've never been banned. I've never been notified of a report, never been chat restricted. What's my secret? I say it out loud. I don't ever, under any circumstance, type it in chat. My cat listens pretty well, that or my wife comes downstairs and rock bottoms the shit out of me and I know my role and shut my mouth.
But even through all that, nobody can hear what I say out loud to myself or friends if I'm on skype or TS. And furthermore, after the game, the first thing I do is ask what I did wrong because I realize 99% of be time, I didn't lose because the enemy champion exists, I lost because I played poorly in some aspect and I need to address that if I ever want to get better. So yes, I do bitch and sometimes I'll even come on boards and make sarcastic jokes about champions, like Soraka throwing Amumu ults at people. But in reality, I know why I lose and I know it's never the champion, it's my gameplay.
So pro tip, vent your frustrations out loud and then go back once you've cooled off and check what you did poorly, it's a great mechanism to never get banned while simultaneously helping you improve. I suggest yelling at inanimate objects, sometimes a laundry basket does the trick for me. Fucking laundry baskets.