I installed this add-on to copy a bit of text from
http://koufukuji.yokohama/analects/764
I thought at first that I had failed (and gave a two star review) because as well as prevent copying, the site changes the selected text highlight colour to a very pale yellow. This add-on works and allows me to copy text from the above page, but it would be even better if it changed the highlight colour to one which I can see for easier selection.