Originally Posted by
Scaeva
It also factors in how good your opponents were.
If you have 50% wins against players with high MMR, your MMR is higher than having 50% wins against players with low MMR.
So it's a bit more complicated than that.
The reason why MMR exists ist so that in the end everyone plays with opponents of the same skill level and evens out at 50% wins.
Obviously what you describe is an effect connected to that. While you climb the MMR-ladder, you'll have a positive statistic, because you did not yet reach the MMR that equals you skill level and therefore face off against weaker opponents.
Similar to what your friend is experiencing, just in reverse.