Would be great if the markings were saved.

Useful, but it would be great to have:
1) Custom hotkeys, or at least the ones NOT COLLIDING with the browser's hotkeys... In Firefox, F9 toggles "reader view", which also resets all highlights and makes that hotkey useless... :(
2) More colors. Why not just let user add custom color using RGB? :)

It works but doesn't save the highlight upon refresh