So we effectively do not trust ladder rating?
No? How do you get that impression?
Inserting a prediction into the match that Trueskill never actually made (by replacing ONLY the opponents rating with their ladder rating) is bonkers!
It seems like there is a misunderstanding here. I'll give you a 2v2 example: When performing the adjustment for player 1 we take the tmm ratings of everyone and replace only player 1's rating with global. Then we let trueskill rate this game and if the conditions mentioned in the first post are met, save the new global rating for player 1. Then we do this with all other players. So for player 2 everyone else will have tmm rating again and player 2's global will be used.
We could maybe perform the adjustment with using only global ratings, but we don't know the global ratings of the players at all. The only thing we know is that their tmm ratings are similar enough to give a balanced game, so we use these. Also we have more trust in the matchmaker ratings than global as I explained above.
I hope you plan to remove global at some point then because if you do it as it is currently planned you are no longer doing things that make sense for having a predictable well-behaved rating system, you are deep inside band-aid mode already.
Yes, I do not believe that global as it is now is a healthy rating system. There are too many variables players can control in custom games to influence their rating. You can see the result in people that are way higher rated than you would expect them to be. Removing global right now would make the gap, setons and astro players rise up in arms, so unless you have an idea how to solve their needs, global stays for now. In the long term people hopefully play the matchmaker more, so global becomes less relevant, but when it has become irrelevant it doesn't really matter if it gets removed or not.
So if i am correct this is the first time we really try to fuck with Trueskill itself!
I really fail to see what we are fucking with. Yes, this change will lead to "communication" between the ratings, but as we all initialize them with 1500+-500 I don't see a problem with that.
The proposed change would also make simulating a change to global rating parameters with past data much harder i think, because global game outcomes are no longer enough to redo all global rating calculations.
Does anyone actually want to do this? This is a genuine question. I know that in the past it was demanded to do this to test changes to trueskill, but to me it seemed more like a ostensible reason to prevent changes to the rating system. There has been a change of the tau value in the past and I don't think it was simulated beforehand with all the rating data we have.
Also, how about we (as a community) discuss such intrusive changes BEFORE they are implemented?
There has been discussion about this. I don't remember everything where it took place, but there was discussion on the issue: https://github.com/FAForever/server/issues/845
We also had a voice call with Morax as the player councillor, some developers and some ladder team members.