Comments are text-based responses that viewers leave on a YouTube video. They are one of the most valuable forms of engagement because they require deliberate effort, signaling genuine interest or reaction to the content. Comment activity is a strong algorithm signal — videos with active comment sections are more likely to be recommended in Suggested and Trending feeds. Comments also contribute to social proof, build audience community, and provide creators with direct qualitative feedback. YouTube comments / shares together form a powerful combined engagement indicator.