#21 - Feb. 26, 2014, 10:41 p.m.
There was indeed a bug with MMR calculations when Patch 5.4.7 was first released to North American servers. We were able to isolate the bug and apply a hotfix for it before the patch was released in other regions, but unfortunately are still a small number of players on the North American ladder who were able to gain some unfairly high ratings before the hotfix could be applied to NA servers.
Fortunately, we've since been able to correct the issue, and affected players should start to see their ratings fall in line with where they should be as they continue playing matches. Furthermore, should a player choose to sit on an unfairly high rating in the hopes of earning end-of-season rewards they would not have otherwise qualified for, we’ll be able to adjust those ratings individually. Otherwise, it’s completely safe to continue playing as normal without fear of any upcoming actions negatively affecting your rating.