Earlier quoted context omitted.
I know nothing about the technical details of font rendering algorithms, but isn't that just an implementation detail? How hard would it be to write a font rendering algorithm that works when each RGB triplet is a vertical line? And having done that how hard would it be to implement a font renderer that switches between the two algorithms depending on screen orientation?
My gut reaction is that well-made typefaces for digital use, which are often designed with hinting in mind, would lose their benefits. For most fonts, though, it shouldn't make a difference whether antialiasing or subpixel rendering is done vertically or horizontal, and I know you can manually specify your subpixel information in Linux. Edit: natesm posted a response to the grandparent of this comment with a screensh…
Eg. 'm' and 'w' would benefit more from extra horizontal resolution, while 'e' would benefit more from extra vertical resolution.