Nothingness: there are some achievements that have stopped working or stopped calculating altogether. I brought it up many years ago and have since accepted that the bugs won’t be fixed. Most achievements still work fine.
(hide) If you want to play a game with an opponent of a similar level, you can define a required BKR range for a new game invitation. Then nobody with a BKR outside this range will be able to see/accept it. (Katechka) (show all tips)