The comment upvotes on YouTube are not generating (direct) income for the authors of the comments, yet even the smallest YouTubers have comments. This is because the incentivization is the content itself (and/or the content creator). People are actually interested in the content and/or in the author of the content.
You are viewing a single comment's thread from:
Comment upvotes works both ways and due to the monetisation of content on Hive, people are also concern on their reputation here.
You can just spam comments on Youtube, writing crap and nothing happens. Try that here and you won't last very long. So content is very important, but your reputation is even more so.
Except that the channel owners may mute/ban you. Some channels even have pre-moderation, which means that they check your comment, before (if) they let it out. Spam is not welcomed nowhere.