We should be able to disable middle click paste for touchpad and mouse to avoid unwanted copy / paste for those who have sensible touchpad and mouse.
It's possible on Gnome :
org.gnome.desktop.interface gtk-enable-primary-paste -> False
Needs a new setting in http://doc.qt.io/qt-5/qstylehints.html
Standard Qt widgets (QLineEdit, QTextEdit) and individual applications (Kate/KWrite, Konsole, Calligra, etc.) need to be changed to respect this setting.
This would be very useful, indeed!
This is really needed and super annoying when you use a touchpad on a laptop, where a light tap around the center is misinterpreted as a middle click and thus unintentionally content is pasted!
I only have found one hacky workaround so far  involving an sxkhd script.
The workaround can break normal control+c functionality in Chromium. There should be an option to disable this functionality.
* sorry, Firefox not Chromium
*** This bug has been marked as a duplicate of bug 441668 ***