I have spent more than 10’000 hours in DotA 2. You do not get banned for a single game no matter how bad you perform. It has to be on a very regular basis, and

I have spent more than 10’000 hours in DotA 2. You do not get banned for a single game no matter how bad you perform. It has to be on a very regular basis, and even then you probably first get put into low priority matchmaking as your behavior score drops. Banning accounts usually only applies to cheats or buying and selling accounts.