Before this becomes another Google bashing session, I'd like to point out that this is one person's opinion, a respectable opinion from an intelligent person but still it's very subjective and a mainly a reactive judgment (see the post's date).
I am subscribed to a number of channels, mainly edu/pop science stuff. I took note to scroll through the comment sections during the change and from what I saw the quality generally improved. I was also pleasantly surprised to see better discourse under some of the more popular entertainment videos although in the first couple of days there was the occasional protest comment. It’s the gaming videos that attract the largest amount of trolling and ASCII art comments.
Ironically those protesting the comments are the ones producing the spam, seemingly just to prove a point. The main complaints: lack of character limit, users can reply to their own comments, and the order of the comments. This isn't unfixable, they'll have to study the new comment corpus and tweak accordingly, there is no one size solution to trolls/spam, just data. And I hope Vi takes that into consideration. The new comment system might need a short while to mature, the fact that it wasn't perfect out of the gate doesn't mean it's a bad concept.
I remember similar amount of displeasure on display when YouTube changed the rating system from 5 stars to thumbs up/down, and there was always the smaller retaliations following each redesign (youtubers hated the new unified channel design at first and produced the mandatory protest videos) there is also residual anger because YouTube nixed video responses late last month due to low usage.
It’s mainly aversion to change, this time the change is bigger and is noticeable not just to those that make the videos.