[2023] Perhaps time for an official transparent explanation for ranked play.. (again?)

How are match rating calculated? (do those stats you see in your profile matter at all?

Are you talking about the champion mastery ratings, like C through S? They're based on performance on your champ compared to others' performance on the same champ (I think it looks at stats like K/D/A and a few other things).

How are MMRs calculated?

If you win it goes up and if you lose it goes down. Purely win/loss based. The amount depends on the MMRs of the other players in your game (if yours is lower than the other players you'd gain more for a win and lose less for a loss and vice versa).

Are match rating influential to MMR or part of MMR's calculations? e.g. Do KDA players overall gain more MMR even if decisions they make lose more games, compared to teamplayers who sacrifice their KDA to win a few more games?

No, performance is not part of MMRs calculations right now.

Do duos/premade have an increased MMR penalty?

In matchmaking, yes, there is an offset to match premades with more skilled players on the other team if we can't put a duo/premade of equal size on the other team.

How fast does MMR recalibrate itself (because at the moment sometimes it fluctuates like crazy, you have one bad game and you match with two ranks below and the next you are matched with you ranks above?)

Variance decreases with games played if you're not winstreaking or doing something else that indicates that you're not being matched in fair games.

Are BestOf3 matches purposefully always gonna habe one high MMR match and one low MMR match?

There is nothing special about matchmaking in promo series. They're also being removed for Split 2 this year.

Is demotion possible? and how exactly can that happen? (current alleged information says if you MMR drops one full rank below lowest division of your rank, you will get a warning and subsequently a demotion if your MMR doesn't improve - does that mean you can win some lose some games, overall lose MMR and drop a rank? or not?

Yes, lose enough games at whatever tier 0 LP.

Is MMR influenced by how well you did in your last season/ your account? e.g. you reached platinum 1 year ago and that was last time you played, would you gain significantly more LP/MMR each match you play?

Yes MMR is mostly preserved even through resets.

How is LP's calculation in relation to MMR?

We have an MMR to Rank mapping. If your MMR is above your visible rank, you will gain more LP than you lose. If your MMR is below your visible rank, you'll lose more LP than you gain. This is necessary to prevent progressive inflation (in other words, the more games you play the higher your rank becomes without actual improvement and the ladder inflates) but it does feel pretty bad experientially.

Is ELO system built into MMR? (e.g. the 50% winrate market invisible hand)

Well, if you are winning more games than you're losing your MMR will rise and you'll be matched with better allies and opponents until you're not. At this point you're probably at the correct skill level. So over time this means people will settle at around a 50% winrate.

Is there a logical measure to bar the contradictory problem of MMR deathloop/ elo hell? (You will an hard match > next one is not FAR more difficult because the system is overestimateing your MMR > you lose that due to MMR being too high (all 9 players are on average several divisions higher) also the 50/50 winrate invisible hand > the game tries to drastically reduce your MMR because how poorly you did in that super hard match (now all 9 players are on average several divisions lower) > now you win that hard > MMR gets super high because you stomped the other team > loop )(difficult to get a balanced game)

We try to make every game balanced as best we can. Plenty of things other than matchmaking can affect fairness or perception of it (are people tired, playing champions/roles they're comfortable with, is one team's draft much better than the other's, did someone lose a 50/50 coinflip play early, did people mentally give up, are people being mean to each other and tilting and playing worse, etc.)

Regarding demotion, so is it possible to get closer and closer to demotion even when at non-zero LP at divison IV of a rank since MMR is behind the scenes to the visible rank then losing just one game after 0LP suddently demotes? Or does it have to be multiple consecutive losses after dropping to divsion IV 0LP.

Could be either, it's really case-by-case. But we try to avoid demotion if we can since we know it's pretty stressful.

MMR being a secret is mostly that we don't show you your MMR value.

Ah yeah you're right!

It'd just be a coincidence. I think we do actually prevent you from being autofilled (neither of your selected roles) in promos. I like the primary only in promos idea but yeah they're gonezo now