Hearthpwn

This game absolutely does not need a report feature.  People who are not on your friends list cannot communicate with you.  If someone friends you and then sends you a message you don't like, you can simply unfriend them and then they cannot talk to you anymore.  This is a perfectly self-policing system with a completely effective user remedy for any toxicity.  Some people seem to just want to have a teacher to tattle to.  

The only toxic behavior that is even arguably a problem that you can't easily solve yourself is roping, and that needs a change to the rules for the rope rather than punishment of players.