so the people who are banned are the ones who get mad for getting trolled? But trolls stay free? .

I have seen a few people trying to contest intentional feeding bans and troll build bans on the forums here, but I personally doubt anybody randomly grabbing and running into/away from enemies when inappropriate with Tahm Kench has been banned. I could be wrong, but it is definitely more difficult to detect gameplay trolls than it is to detect chat offenses.

EDIT: They are also less visible. Generally people who were banned for gameplay offenses know what they were doing, so they don't really have any subjective ground to stand on. A person with a chat offense can often feel the punishment was unjustified due to their unique outlook on the media. This causes them to make a post on the forums for debate. However, because a gameplay troll generally doesn't have anything subjective to argue they don't even try.