I think people tend to downvote out of negative emotion but more likely upvote out of genuine interest. All it takes is one bad actor to downvote a comment earl

I think people tend to downvote out of negative emotion but more likely upvote out of genuine interest. All it takes is one bad actor to downvote a comment early and it may never again gain enough visibility to get the position it actually deserves. On the other hand, the absence of upvoting keeps the comment at a neutral level. Its speed of losing visibility can't be unfairly accelerated, and so it has a chance at competing with comments of the same level.