I have noticed that on Blur+ 5.2.3 - Fabric 1.21.9, the config does not get read or modified when values are changed in-game. Setting values in the config, does not make the mod read those values.

I have not tested in 1.21.9, but it might also be the case there.

Also the case in 1.21.9. Came to report the same thing. Figured it might be because I didn't have MidnightLib installed but it didn't fix the issue. Nothing seems to get saved, nor does altering the config file directly do anything. Huge oversight potentially. Although I find it strange that with 4 weeks and 50k DLs that only two instances have been reported... some specific issue maybe?