The original change (9adcebd3c2e476c8a32e9b455cc99f46b0e12a7e) to prevent sudo usage broke the use case of running KWrite or Kate while logged in as the actual root user with a GUI session. This is how the Kali distro is set up by default, so the original change amounted to making Kate and KWrite not launch at all on this KDE distro.
This patch re-enables running as the actual root user, but keeps blocking usage via sudo or kdesu. There are no negative security implications associated with re-allowing usage via the root user, since if you're running a GUI session, you were already exposed to the original security threat and Kate and KWrite do not increase the attack surface.
I have submitted a similar change for Dolphin that has been accepted (D12795), but @elvisangelaccio wants that to go in at the same time as this, to keep them in sync.
BUG: 387973
FIXED-IN: 18.08.0