> there's no support for getting subpixel order in X.
> Subpixel rendering allows to draw better looking curves by taking into account the fact that physical pixels on the screen consist of discrete subpixels.
Here you're wrong. Twice. Both X11 and Wayland provide that information. But the fun part: it is useless in Wayland. By design. Because in Wayland your surface could be rotated, stretched or somehow transformed, so that subpixel information is completely useless there. That's the Wayland protocol with its great "reliable" design.