See, I don't see that as a user. The bad comments sections used to be full of bad puns and arguments, but now they're just smaller and full of contentless "watch this" mentions. On channels where the comments used to be good, they are now rare and inaccurate.

The "watch this" mentions are something different - that's Google's way of trying to make things go viral (or something like that) on their social feeds, and I believe is completely unnecessary.

I believe they're just comments pulled in from google+ threads that mention the video in question, based on the logic that all comments on the video should be grouped. The problem is that people don't actually comment on videos on google+, they just share content.