I have to agree with Joshua -- programs like marble or kdenlive work just fine without systemd, but this dependency keeps them from doing so.
Since I have a couple of boxes that are pretty heavily tinkered with (which makes them unattractive for systemd), I just tried it, apt-get source-d libpolkit-qt5-1-1, removed the libpam-systemd dependency in both places in debian/rules, built and installed the package, and the (few) kde applications I've tried installed and ran without problem. So -- it may be that some component of kde actually depends on systemd, but given the wide-ranging consequences of this particular dependency (essentially shutting out non-systemd boxes from KDE applications) it'd be great if the dependency could be limited to that particular component.
