Yeah they’ve experimented a lot with this stuff:
Lead producer Travis George was fearful the game’s reputation was hurting its appeal and stifling growth. “Nobody wants to play a game with somebody who’s mean.” George was quoted as saying. To change player behavior, Riot Games formed a working committee George called, “the PB&J Team, which stands for Player Behavior and Justice Team.” The team included two PhDs, one a cognitive neuroscientist and the other a behavioral psychologist. The group employed concepts similar to Bandura’s and built a variable social reward mechanism into the game.
The system was designed to curtail bad behavior by allowing players to report users for “unsportsmanlike” conduct. Offending players were judged by their peers in a “Tribunal,” which company President Marc Merrill is quoted as saying helps players, “recognize that there are consequences to their actions.” Referrals to the Tribunal are made public and the company emphasizes that, offenders lose games!" making them social outcasts others avoid playing with.
To reinforce teamwork and helpfulness, the company also instituted a rewards system called “Honor” to “identify … pillars of the community.” Honor points became viewable to others players and were awarded or revoked by members of the player’s own, or opposing team. Since implementation in late 2012, Riot Games has reported a dramatic reduction in adverse behavior and a noticeable increase in helpful actions.
I have a hard time keeping track of what they’ve tried last, and a few things they tried they did not keep because it didn’t work well. Of course, experimentation is key.. and it’s not just discouraging bad behavior, but encouraging positive behavior alongside that.
These are the two most recent ones, I think:
http://www.polygon.com/2014/7/21/5924203/league-of-legends-ban-code-2500-toxic-behavior-permabans
http://www.polygon.com/2015/1/6/7500045/riot-games-league-of-legends-bans-rewards-behavior