See here https://discord.com/channels/549281623154229250/1228467265096384693
The match rating of that player is likely negative but they only see 0.0 on the website causing them to think the rating system is bugged. Similarly when they run $whoami they only see 0.
A potential improvement would be making a tooiltip over 0.0 to show the true negative value (skill - uncertainty = -negative number) https://server4.beyondallreason.info/battle/ratings