As far as I can tell it works, but unfortunately, it also makes me unable to pause any video without refreshing the window. So I'm going to have to say this is not what I'm looking for, as that trade-off is not worth it.

It actually pauses the videos, but it does not allow neither YOU to pause a video.
¿?¿?

Meddles with more than simply countering the still-watching? question. Caused playlists to move on to random videos despite the setting causing that suggesting it didn't function on playlists, then paused the next video on the playlist instead of letting it run. Too annoying.

Has stopped working

Works well. But it consumes a lot and slows down the browser.