>> The second problem is less important to the extent that it only affects
>> proprietary operating systems, AFAIK, and it can be solved by installing
>> additional Free Software (mostly Ghostscript).
> The second problem is simply irrelevant: if the printer supports
> PostScript, the OS is not important, because all modern OSs support
> PostScript printers.
By "the system" I mean "the hardware & OS on which Emacs runs".
For Emacs to be able to print, the system (either the printer or some
part of the software) needs to support Postscript.
Printers that don't understand Postscript are still pretty common,
AFAIK. And Windows doesn't provide Postscript support for
non-Postscript printers unless you install ghostscript. So it's
not irrelevant.