Gameplay trolls do get punished. It's just that it's more difficult to track and detect at times since the system has to be sure that the person in question is actually trolling rather than just having a bad game or two. Don't believe me? Well Here are two examples of gameplay trolls being banned. Yes it's just two examples, but it proves that they do get punished. Regardless though someone else acting up doesn't mean that your own poor behavior gets a free pass. If you reported them and they have a history of acting up like that then they will be punished. From Understanding the Tribunal:
4) That player in my game was far worse than me. Why am I banned???
a) I'll keep this one simple: retaliation isn't OK. Reacting to a toxic player by being toxic just incites that player to be even worse--it also ruins the game for up to 8 other players. It is far, far worse to watch two people yelling at each other all game than it is to watch 1 player ranting into blank space. Almost everyone in the game can find someone out there that behaves worse than they do--but so what? Finding someone worse doesn't justify your behavior or justify retaliation. We expect more out of our players. What players often don't realize is... those other players in your game that you thought were worse? Nearly 100% of the time, those players were banned even before you were. If someone is being toxic, just report them and move on. If you retaliate, both of you will be banned. It's really that simple.