Cuthbert only provided a single developer statement in the overview section of his opening post.
Overview
Overwatch’s designers say they “balance” matches with MMR. The system sorts the twelve players from each match into teams, based on the merit each player has shown in matches past. Matchmaking uses merit-tracking algorithms (MMR) to keep matches from being ‘uneven.’ Principal Overwatch Designer Scott Mercer explains:"When the matchmaker creates a match, it determines the % chance for each team to win based on the match it made. The VAST majority of matches are usually near to 50% (especially if you’re a player closer to median skill rating and you’re not in a group). When we do put you in a match that we know isn’t a 50/50, we adjust your SR gain or loss based on your calculated change of winning.
"We model the synergistic effects of players being together in a group. Based upon the data we see in groups, we predict the win % for each team. We try to match similar sized groups together.
"The amount of MMR (and SR) you go up or down isn’t simply a matter of whether you won or lost, and what was your predicted chance of winning. There’s a couple of other things at work. One is the matchmaker’s confidence in what your MMR should be. Play a lot of games, it gets more certain. Don’t play Overwatch for a while, it gets less certain. You go on a large win or loss streak, it gets less certain. The more certain the matchmaker is about your MMR, the less your MMR will change in either direction based on a win or loss.
"We also do evaluate how well you played the heroes you used in a match. The comparison is based on historical data of people playing a specific hero (not medals, not pure damage done), and we’ve done a lot of work to this system based on the community’s feedback.
“While it’s a minor factor compared to wins/losses (The best way to increase your SR is still to play together and win as a team!), doing so does help us determine your skill more accurately and faster.”
Notice how he does not link to the source of Mercer’s post though. The reason he does not is because Mercer was not trying to say that they distribute the good and bad players evenly at a given SR for a match (I don’t even know how you can read that as such).
Below is the source of Cuthbert’s Mercer quote. The topic was about why matches had some weird groupings such as 6-solos vs 2 3-stacks or 6-solos vs 3-solos and a 3-stack, and the resulting SR gains/losses. It had NOTHING to do with any kind of handicapping.
Kaawumba has collected all Blizzard statements on how Competitive and Matchmaking works in his topic, so go there: