My platform is Manjaro. The following behaviour can be reproduced with Kate or LO-Writer, for instance. There are occasions where I want to cut the first part of a text line into the clipboard, then delete the rest of the line, and then copy the clipboard into another document. I can do it most of the time but, if I start to speed up, the clipboard starts getting the end of the line that was deleted and not the part that was cut. Reproducible: Sometimes Steps to Reproduce: 1. In a text editor, write a sentence with a few words. 2. Select the first few words with the keyboard using Ctrl-Shift-RIGHT. 3. Next, we'll cut the selection, then select the rest of the line and delete it. *Quickly*, press Ctrl-X, then press Shift-RIGHT, then press DEL. 4. Press Ctrl-V to see the clipboard content: if it was done fast enough, it will be the deleted portion.
Step 3 should be: *Quickly*, press Ctrl-X, then press Shift-End, then press DEL.
I reproduced this in Kate. However, I also reproduced it with plasmashell not running. Therefore it's not a Plasma problem. Sorry.
You think it's an X thing?