Ability with toggle in settings to make 'watched videos' in history appear slightly greyed out, like when you are searching for a new video to watch and you wonder if you already saw it or not. Sometimes the orange bars are not real apparent, or only show a little nub that do not grab your attention. I know you are into aesthetics, but a toggle in user settings may make it optional for some users. I personally would find it to be very clean and useful addition to the site, could look nice if done subtle too.
