They redistributed the ranks today so that they confirm to a normal distribution bell curve now (they didn't before and both the top and bottom ends were too populated). I was prepared for a demotion this week, so was confused when I actually got a small promotion - but it turns out after considering the redistribution I did indeed still lose MMR this week.
That being said, we know that the algorithm does look at more than just wins and losses. Valve themselves confirmed it looks at the players you've played with and against during the week and how well they did in subsequent matches. Some form of individual performance metrics does also seem to be in play (getting post-match medals seem to be good for example). Consistency is also more rewarding than single standout games. Finally - albeit anectodally - it looks like win and loss streaks matter a lot. This was true in unranked too: big winstreaks could really catapult you. I know for the weeks where I lost rank I've had loss streaks, for instance, even though my overall win rate wasn't that much worse.