Hi,

this seems rather strange to me:

When I open the "PolicyKit Authorization" module in systemsettings and click "Modify" on any property, a Gnome (gtk+) dialog appears and asks for the root password.

I'm just wondering why a Gnome dialog is displayed within a KDE application.

Our desktop experience is becoming more complicated day by day...

Did you have installed Gnome destop?
It`s beacause possibly the two destop exist in your OS together.
Sometimes,they have some problemes in compatiblity.

I never installed the full Gnome desktop, but I probably have some Gnome libraries around that were installed as dependencies for other applications.

"policykit-gnome" for example was installed with networkmanager.

The GNOME PolicyKit manager was likely already running, so there was no need to start the KDE PolicyKit manager, since both are capable of performing the needed task of requesting the password.