>Fractional scaling is exactly what we're talking about. ... That's circular. You're arguing that the way things are done is an argument for things to continue to be done like that.

Actually no, what you are describing is ideally having no scaling at all in the compositor on any particular monitor. (Unless of course a window is stretched between them) I'm not arguing for things to be done any way, I'm saying don't misuse a feature that was designed to do something else than what you're asking for.

For a vector UI that is supposed to be pixel-aligned, you can't render that at a non-integer scale without the same blurriness that you would get with doing the scaling in the compositor. That's different from rendering print content that has no relation to pixels.