Positive feedback is feedback that makes more people see a post.

Negative feedback is feedback that makes fewer people see a post.

This is intuitive for votes, but counterintuitive for replies.

A reply on 4chan bumps a thread to the frontpage. A reply on tumblr or a "quote retweet" on twitter shows the post to your followers.

All these things are positive feedback, regardless of whether they express approval or disapproval.

Of course most people would dislike angry replies and "quote retweets". But the character of a platform is not determined by most people. It's determined by people who are attracted by it, and succeed in it.

Vote-based feedback loops like reddit, encourage conformism, reply-based feedback loops like 4chan, encourage trolling. Reddit and 4chan are pure examples of one type of feedback loop, but twitter combines both: Likes and retweets encourage conformism, but the "quote retweet" encourages trolling.