So I just checked a couple of the accounts mentioned, and they are indeed inactive for the last few months.
It seems they’ve managed to find a hidey-hole in the matchmaking table that almost no other players are qualifying for, so they’re not being cleared out.
The 2.0 matchmaking system will take care of that for sure, since it will be refreshed every week!
In the mean time, I might see what we can do about clearing them out.