I knew middle click pasted, but just learned what it pasted.
Since making the move to Linux in '16, everyonce in awhile was getting what I thought was odd behavior by using middle click so I moved purely ctl-v.
Come to find out highlighting with no copy command plus middle click paste will paste what is highlighted.
I personally find that cursed behavior, but I can see how its useful to reduce total overall actions.
Today I learned.