Reason: I am using Linux and there you can copy/paste with ^C/^V and you have a second copy/paste buffer with simple select and then insert with the middle mouse button. This second copy/paste is very useful when you want to copy two text parts from another browser tab.
Problem 1: Copy/Paste with the middle mouse buttons does not always work. Problem 2: When copy/paste with the middle mouse button at a certain position, the text gets inserted at the cursor position, the usual behavior is at the mouse position.
A seldom problem: When you write an answer and use some <pre> </pre> block, it seems to get garbled, at least the preview just below does not look as expected.