Blizzard has said that it has implemented a change for Competitive Play across all versions of Overwatch whereby skill rating at the end of a match won’t be affected by players leaving in the middle. Over on Battle.net, Community Manager Lylirra explained how the update will prevent players from being tempted to “troll” a winning team by leaving. 

Previously, if a player from either team left mid-match, the game would automatically recalculate each team?s probability of winning, taking a look at not only who left the match, but also when they left. The assumption was that if a team was a person down, the odds of them winning would go down, too, and that the most accurate thing we could do was account for this when adjusting each player?s Skill Rating at the end of the match. Despite being more accurate, we received a lot of feedback that this recalculation just didn?t feel great and that it incentivized bad leaver behavior?which is last thing we want to do in Competitive Play. As a result, the game will no longer recalculate each team?s probability of winning whenever one or more people leave. This means that your Skill Rating will always be adjusted based on your team’s odds at the beginning of the match, even if there are leavers on your or the enemy’s team.

We’re told that the change will make skill rating adjustments a little less accurate in these specific matches but it should “remove the incentive to troll a winning team ...