@bruce Agreed. Once you get used to it, middle-click paste is hard to shake. I still try to do it on Windows work PCs and look confused when it doesn't work.
Trouble is, I don't think gtk apps have done it properly for years. I think the semantics are supposed to be that if you click on somewhere with a caret, it leaves the primary selection intact. So you can highlight some text, reposition the cursor, then middle click to paste. Gnome apps seem to clear the selection when you do this.
@vkc

@lokjo Is this not just an OpenStreetMap frontend?