> I’m not sure how this works but I use Mail’s filter for my aggressive filtering and I also use Gmail’s filter for general purpose pre-filtering. It seems to me like I’m free to do whatever I want with my own filter, but maybe I’m marking mail also for Google as spam if I move it to the respective folder? I wouldn’t want to do that.

Oh, in Mail it might be different if Apple doesn't use that data to train it's default filter. Which seems unlikely.

I guess I don't know if Google does, I just assume they do because they're data junkies.