1) Any idea what's responsible? 2) From what I can see the issue isn't just startup. If you see my previous email, it looks like the notifyd is crashing for some reason.
Maybe, xfce4-notifyd crashes on startup due to not set DISPLAY environment variable?
Please, check for DISPLAY using: dbus-update-activation-environment --verbose --all
If not, make sure /etc/X11/xinit/xinitrc.d/50-systemd-user.sh gets sourced on startup of Xorg in some way.
