I think matchmaking is not properly implemented yet. Seems like they just match you up with anyone that is also in the queue. Is there even a way to lose rank? So far I haven't seen a way for that to happen, you just gain rank as you win.
You lose a skill point every time you lose a match. I can't remember if that's true for carbon of they don't start doing that until bronze rank though.
Oh so that's how that works. I just hit bronze two days ago and haven't played since. I can confirm that I haven't lost a point for losing while in carbon though.