When using the mouse based window activation (option 3 or 4 from the left in the window behavior dialog), an active krunner often closes when moving the mouse and thus activating other windows while using Wayland.

This does not happen (ok, it happens, but only rarely) with X and I think it should neither happen with Wayland.

Test:
Open window on left half of screen. Open window on right half of screen. Open krunner using a keyboard shortcut. Move the mouse multiples times between the left and the right half of the screen. Then krunner closes although it should stay open unless the user clicks.

BTW: Kudos to your progress in Wayland's stability! I could write this whole report in Wayland without a single crash which was not nearly possible on my system some months ago!