Can't you just programmatically see when they are taking a screenshot and provide them a clean frame (Micropause of all drawings in this case). I mean you could experiment doing all sorts of stuff, like instead of a clean frame, you could black the whole screen for that microsecond, the user would barely see anything but a flicker, i mean would they really ban someone for a black screen, that seems like a super weird detection vector to have to magically line up the current frame and frame taken. I would assume the screenshot is scanned with some kind of machine learning tool that has been trained with ESP displays and menus, so black should be like an inconclusive malfunction.