The company even set up a server that helped it find out if players saw the endorsement system as responsible for the drop in hostile behavior, and the perception was "close" to reality, Miller said.

This isn't to say that Blizzard's achievement is flawless. It's not clear how many instances of toxic behavior there are, and a 40 percent dip still leaves a lot of players causing grief. Still, it's a start -- and it might show other game developers how they can create a welcoming environment by changing attitudes, not just by banning offenders.