MiG-21bisJwBtw, I was testing 8k for fun earlier and on an MGE server with 2 players there was 0 noticeable stuttering, but when I switched to a 6s pug it started stuttering. So idk what is up with the engine.I can only guess its because tf2 doesn't do a lot of splitting CPU tasks between multiple cores, so when you are in an MGE server, there is a lot more CPU headroom for your 8k polling, but 6v6 pushes your CPU too hard that 8k doesn't work well. I think more modern games can perform mouse input calculations independently from other calculations.
While TF2 is basically single core bound I don't think that's the problem at play here. In my testing my 5800x3d machine can handle up to 4k polling before it noticable studders. But on my overclocked 9800x3d rig it heavily studders at 4k, somewhat studders at 2k and is fine at 1k. This was tested between three different mice on an empty 2fort server hosted on another machine. I even tried different USB controller configs (controller connected directly to CPU vs PCH) and got the same results. I don't know what else I could rule out other than source spaghetti really at work here.