In Krunner on P5 currently the whole line (with the category) is highlighted, although the selection actually only belongs to the item in the right column. Further discussion with mockups on the VDG forums: https://forum.kde.org/viewtopic.php?f=285&t=125741 Reproducible: Always
The suggestion in https://drive.google.com/uc?export=view&id=0BzSEgMDlhzW3Y2VsX2RET3o1dFU seems interesting. Currently it is a bit wasteful to display the same category over and over again.
I like that mockup. Looks good.