The explanation I was given is that the scoreboard orders by rank, then score. Ranks only periodically get updated, so in between updates it's entirely possible for someone who's doing better recently to have a higher score because they haven't gotten promoted over the person above them yet.
When the pass for ranking occurs, then it gets ranked based on score and reorganized.
Someone please correct me if I'm wrong.
You are correct. Someone with a higher score than someone else can be on a lower position, simply because he wasn't promoted yet to the next rank. However
, the actual bug is, that within
the ranks, the sorting is wrong. As far as I (and sirmonkey) observed it, the sorting within the ranks is based on the order of promotion. So consider the following example:
At Rank PVT/WR, all players are still sorted correctly by their score. Player C now gets promoted, because he has the minimum points required for the next rank.
Meanwhile Player C and Player A make 30 additional points each...
...which makes Player A reach over the minimum points required for the next rank as well. What happens now in MW:LL is this:
The players are sorted by rank, but within the ranks, player A is placed above the other players with the same rank, because he was the last to achieve that same rank. What should happen though is, that players are simply sorted by their score, within their ranks instead.
This was already reported some time ago: http://forum.mechlivinglegends.net/index.php/topic,15861.0.html - Scoring appears to be illogical (?)