If you queue up for a SOLO game you better play it SOLO, and do not group up with one, or multiple friends. Just like every other rule, this will reward you with a permanent ban.
Should be obvious.. i guess?
While you can leave matches by typing !leave in the chat, which will start a countdown and afterwards disconnect you without penalizing, simply leaving the server after the round has started by yourself is penalized with a temporary queue ban if you are a repeat offender.
This one should be obvious. Any external assistance is punished with a permanent ban. Period. I don't care if you are only using a bhop script or some kind of cheat. Abusing bugs is a similar thing, it doesnt matter if the bug is "widely known". If it gives you an unfair advantage don't use it if you don't want to risk a ban.