Hi Brendon, I was working on gnome in the meantime, so I only noticed your remark today.
I checked my /etc/X11/xorg.conf.d as you suggested, but there is absolutely nothing in there. Long time ago I remember having tried to set up a second X server to get bumblebee working, but I gave up on that. My attempt to fix the kwin_x11 behavior basically had me remove the entire kde-stuff and everything remotely related to intel graphics as well. In the meantime I am also back at testing rather than unstable. The kwin_x11 issue is still unchanged. Currently, I am in the process to disobey the debian rules for bug reporting and to cross-post at kde. Thanks for your update, Happy Christmas/change of the year/may reason be with all of us... Stefan