> Nobody uses core X, he says. My Emacs disagrees, it's running on a headless server using network transparency, plus client-side fonts, right now and working quite happily with very low volumes of network traffic and effectively instantaneous screen updates.
You've just proven the point. Emacs uses client-side drawing and client-side fonts, like everything else these days. The only relevant applications left using core X drawing/font/etc primitives, or anything other than windows and pixmaps, are the X test suites.