X (at least nowadays) isn't very network transparent. Most things are done via shared buffers (it's faster than shoving bitmaps down a socket), with special fallbacks implemented by the clients, so that x forwarding doesn't break.
I know, also font rendering with anti-aliasing is usually done on the client side now (though the old way with font servers was far from ideal, it was much more bandwidth efficient!).. I know it's not perfect but they do this because the protocol lacks support for smooth video.
I'm just advocating a modernised X over moving to Wayland altogether, like the poster I replied to.
