The "Close" tooltip used for the window decoration's close button will appear frequently when not hovering over the close button, and when hovering over Qt application widgets which don't have their own tooltip. I can't reproduce this behaviour under X.
Cannot reproduce - could you please add more info about your system? Plasma: 5.13.2 Apps: 18.04.2 Frameworks: 5.47.0 Qt: 5.11.1 Kernel: 4.18.0-1-MANJARO OS: Netrunner Rolling Video: Intel 4400 Driver: xf86-video-intel 1:2.99.917+831+ge7bfc906-1 Mesa 3D: 18.1.3 Screen: 1600x900 Xorg: 1.20 Wayland: 1.15.0-1 Wayland Protocols: 1.14-1
I don't know what commands you used to get all that information but here's what I could gather: Plasma: 5.13.2 Frameworks: 5.47.0 Qt: 5.11.0 Kernel: 4.13.0-45-generic Video: Intel HD Graphics 520 Kernel driver: i915 Mesa 3D: 18.0.5 Xorg: 1.19.6 Screen: 1920x1080
There were many improvements wrt handling of internal windows and I cannot reproduce this bug. If you're still able to reproduce this bug, please reopen the bug report.