The recent change in the YouTube comment system, more specifically, the merge with Google+ has created a tremendous amount of backlash.
Top YouTubers such as Yogscasts, Nerd³, Totalbiscuit and Pewdiepie have disabled comments all together on their new videos, one citing increased spam being submitted to their videos.
"Due to the recent changes of the YouTube comment system I'm forced to disable comments. Since front page/top comments are filled with: Links to virus sites, Advertisers, Self Advertisers, Spam, Copy and paste pics of dogs"
"Feather" is an inbuilt YouTube project which cuts down on all of the excess layouts and javascript to deliver a faster YouTube experience. Dedicating the entire screen to your chosen content instead of sidebars.
One side effect benefit is the complete removal of any and all comments.
The comments rarely add anything of value to the video you are watching and most of the time end up being an argument about something totally unrelated, so for me they won't be missed at all.
However, YouTube have added an option to enable comments on a single video temporarily just in case you wanted to dive into the comment cesspool.
Happy YouTubing