Round 5 gave me an idea about how strength pairing works. Note that I’ve divided the players into “groups” by points.
First, the close pairs of crossed lines (in the 3-point group) came from players changing rank over the few hours since this rounds started and when I grabbed the screenshot. So don’t worry about those.
But why is the #1 player paired with #4? And what could explain those huge jumps for the Smaug-yung_catnip and Lys-mark5000 matches?
Maybe it works like this: starting at the top, the algorithm considers one group at a time, pairing closely-ranked players within the group. If there’s someone left because the group had an odd number of players, he gets moved to the next group down, but placed in order by sitewide rank, ignoring tournament points.
For example, Smaug1 was left out of the 3-point group pairing and moved down to the bottom of the 2-point group. But then Lys was left over from that group and moved to the #2 position in the 1-point group, so he eventually got paired with the #1 player from that group.
That explains the big jumps. But then how are players paired within a group? It seems like it might have to do with how close the ranks are, and maybe it tries to avoid repeating pairings from previous matches, but I can’t think of a story that would explain everything.