Already mentioned in this thread is the fact that for videos with high frequency comments, reading vertically scrolling text becomes impossible because they scroll too fast.

Would would be cool if video platforms allowed Reddit-style voting for 3 or 4 comments per 10/15/20 second segments that would display as bubbled up (with viewers being able to expand for more comments for the same time slot).

That would solve the issue of comment-spam overwhelming the videos, plus it would become an incentive for higher quality submissions.