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Some conclusions about Matchmaking and Brackets in General Discussion
Quakeman
    After reading several threads about how does the mm works I decided to add something to this community.
    Let’s begin:
    2 years ago I Started to play Dota 2 on this account:
    http://dotabuff.com/players/86755844
    http://pubstats.me/86755844/
    In about 4 months I got into high bracket, and there I stayed more than 1 year. That’s when I started a Smurf account to play with my friends that were playing for the first time. That’s the account:
    http://dotabuff.com/players/120461140
    http://pubstats.me/120461140/
    In this account, I was the best player on my team, most part of the matches. So I started to play like someone who it’s always on his on, I mean, I would Ks, no matter what Hero I was playing, stealing farm from the carrie (not proud of), and then Boom! Very high games started for me. As you can see, win rate is lower than 50%, but very high bracket was achieved.
    Then, I came back to my old high level account 2 months ago (cause of Steam summer sale), and I believe I came back a better player. Put aside my addiction to ks (haha), and started giving my best for the team according to my hero. In 1 month, very high games started to appear.
    Conclusion (my opinion, of course, you are free to disagree): KDA is one of the most relevant aspect Dota 2 takes in consideration, comparing your KDA to the global average KDA at the same hero. If you are playing support, more assists will get you more points, less deaths too.
    The second most relevant aspect is GPM/XPM, again comparing to the global average. My point is, I just went into very high bracket when I improved these aspects, implying that those are extremely relevant in allocating you to some bracket.
    Sry for the bad English.
    Ty, GLHF!
    God among peasants
      i thoguht soo too and it would make sense especially if u consider that sing sing was highest rated player at one point while he always farms and go for kills even with randomed supports

      also few players on devs dota 2 forum said u can reach very high bracket without winning a single game only thing u had to do is reaching good kda

      i believe it was ranaki that tried that 0 win thing with new account
      This comment was edited
      kord1g
        I play like 3x my allies every game and i still play in high only. Nor that i want to play very high (me solo against stacks, no thanks), but just bringing up that this brackets sometimes are very random imo.
        God among peasants
          i am sure mm has same shit alghoritm as old report system L:OL @ We are looking at patterns of behavior over time only
          2 reports in 24h put in nice words
          pretending to be competent is what valve does
          This comment was edited
          ✖ Chains ✖
            so what if u troll a bit ig when u won and suicide sometimes it makes u unskilled for valve ?
            i doubt they are that retarded ;>
            God among peasants
              yeh clearly report/mute system didnt show that
              God among peasants
                and other things they designed that didnt work at all like hero performance bars ( both editions ) hall o fame and guilds
                God among peasants
                  and even gayben said they have shit rating system
                  ✖ Chains ✖
                    im not talkin to you ? ;o
                    God among peasants
                      yes you are
                      Sōu ka
                        what most people don't understand is that in some games you are actually expected to do really well especially when you play a carry

                        for mm having a win rate significantly higher than 50% means that you are underrated
                        mmr can be seen as an expectation of your performance in the actual game and when you feel like your game is rather low rated (by your own standards) and you're being one of the best players you should accept that it's expected for you to crush the enemy players as they'll be worse on average as well


                        _mcc
                          I've been working my way up in the brackets.

                          When I finally get to the very high:
                          http://dotabuff.com/matches/308329784

                          Guy playing his first lion feeding ultra hard, a poor mid by me and a clueless alch.
                          In the next game I was back all the way to the NORMAL bracket.

                          Wtf? Is the team performance taken into consideration?
                          [Lk].Zano
                            Maybe it considers the past few games?
                            I don't know, it seems to be a very random system for me.

                            Here are my last 4 games:
                            http://dotabuff.com/matches/303738122 VH game with one leaver in my team. Lost
                            http://dotabuff.com/matches/303764084 Another VH game but this time with 2 leavers in my team. Lost
                            http://dotabuff.com/matches/303779666 Third VH game in a row. This time against a team who didn't know how to deal with a Huskar.
                            http://dotabuff.com/matches/303805383 This game followed it. Compared to the first 2, I think I did a decent job in the third game, but I was still put back into High bracket, which I wasn't put into after 3 loses in a row.

                            So...unless I was demoted from VH for picking Huskar, I could say that it either considers not your last game but the last few, it is a very random system or the High bracket and the VH bracket are no different at all.
                            HeLL_RAISeR
                              So when I play naga support my MMR decreases because most of the people play carry naga and my KDA GPM XPM will be lower than the average?
                              BULLSHIT
                              This comment was edited
                              way2high
                                When you are switching between high and very high, it probably means you're in the high end of high and the very low end of very high.
                                HeLL_RAISeR
                                  let me tell you something. I got a losing streak few days ago and went down to the normal bracket.
                                  http://dotabuff.com/matches/299956404
                                  this game started TERRIBLY, godlike viper godlike QOP, The score was like 2-22 on minute 20 with my teammates feeding ( I had 0 deaths at that point) . But I kept on farming calmly, got 2 kills on my lane and farmed desolator and blablabla. so the plot is, I carried the team from the bottom of the ocean. Their win looked safe but I still carried them hard.
                                  So after that game I was put in the very high bracket from normal. one game shouldnt affect my mmr drastically because I had 100+ games at that point. But it did.
                                  So I mean that there are a lot more things that MM uses to calculate your mmr.
                                  This comment was edited
                                  HeLL_RAISeR
                                    another example
                                    http://dotabuff.com/matches/308597828
                                    safe-lane medusa. we won early game and started pushing. but after some point I left them and went to farm jungle. so they were playing 4vs5 from that point. So even I didn't die a single time and had respectful KDA. I still got down to high bracket game after this one. maybe because my K+A was lower than any of my teammates. who knows.
                                    way2high
                                      Was there a leaver in that game? As soon as there's a leaver, any game will be considered normal.
                                      way2high
                                        Like I mentioned earlier, you're probably in the high end of high and low end of very high. This is why you're bouncing back and forth because its virtually the same.
                                        Sōu ka
                                          if you solo queue you might end up being used as a filler to balance 4 and opposing 5 man stacks or two 2 man stacks
                                          especially when you queue at odd times
                                          if you are in the middle of high or something i could imagine that you could be used to balance both normal and very high games

                                          your mmr actually changes rather quickly since you have a very small amount of games and kda is an important factor in that matter
                                          Quakeman
                                            I wonder if they consider the number of wards you buy if you are a support, that would be interesting. Or the Apm, usually pro players have a higher apm, right?
                                            Relentless
                                              The highest apms I have seen are often on very bad players who click a ton of times to move and attack for no reason. When you watch the POV of pro players they use very few clicks because they only do what is needed. Their apm would actually be lower than average....and that is why dota does not track apm. It is not a game where there is often more to do than it is possible to click.

                                              I think OP is right that KDA does have an impact on MMR. I don't believe that it should but there are just to many examples indicating that they do use it. I suspect that it is used to change the uncertainty variable that determines how much change in MMR you get for each game.

                                              As for GPM...what is needed to test that is a smurf account of Alchemist who farms like crazy game 1 and instead of winning right away just goes for 1000+ gpm. See if he jumps to Very High like a huge KDA score would. To be an independent test you have to have super high gpm and low KDA. Just PVE it and then get some towers.
                                              This comment was edited
                                              Papa Het
                                                KDA is probably the only thing affecting MMR. A friend of mine made smurf, went 41/0 with pudge the first game and was in very high ever since. His winrate is even lower than mine at the point of 60 wins and I haven't seen a single game in high.

                                                Sometimes he wins a game with his smurf and drops down to high. Then he loses and gets back into very high again. The MMR in Dota is very, VERY weird.