Fantastic idea for an add-on! I totally recommend this.

Bugs/Issues I found (Version 3.1.1, Firefox Windows 10 ver. 71.0):
- suggestions/comments still show if a video is accessed from outside of youtube (google, whatsapp, pasting link, etc.)
- suggestions/comments still show if a video page is refreshed (e.g. to fix buffering), or accessed by pressing the previous/next page buttons
- suggestions/comments still show if a video page is accessed via the suggestions side-bar (that shows up because of the above points)
- once suggestions/comments show (while blocked), they won't disappear until you close all youtube tabs, and access the site again from the homepage.

Suggestion:
- Have an option to disable youtube autoplay as well (as it's another distraction)