There is literally 0 point thinking about MMR. You have zero control over it and as you say, Blizzard themselves probably don’t even know how it works.
The only thing worth remembering is that every time you don’t play, it gets easier to climb. If you tilt or feel you’ve got stuck for 20 games, just stop for a week and when you come back the MMR will have moved a bit and you’ll get some momentum again.
You see, the right side of the tank is filled with mmr and cr balls…
The Blizzard Manatee will pick one and bring it to the other side of the tank where the playerpool is.