Hover a thumbnail on youtube.com and click an icon at the right: "Not interested" and "Don't recommend channel"
< Feedback on YT: not interested in one click
Maybe in the future. The thing is, adding such a functionality should be optional so I will have to add a configuration which I dislike in general as I try to keep scripts simple.
thanks, works great! Would it be possible to add a button that does "Not interested" -> "tell us why" -> "I've already watched the video" automatically?