There has always been a reporting system for bad behavior and it will remain in place in Overwatch. However, Blizzard is also introducing a new Endorsement System that will allow players "to acknowledge other players for having a positive impact on your gaming experience". You'll be able to acknowledge your fellow teammates who are as invested in having fun as you are.
In addition, the Looking for Group feature is now part of the game and it allows "like-minded players" to queue together to "make sure you have the kind of Overwatch experience you want!"
Read the full post on the Overwatch site.