How do you go about determining what is collaborative or "bridging" discourse, though? That seems like a tricky task. You have to first identify the topic being discussed and then make assumptions based on past user metrics about what their biases are. Seems like you would have to have a lot of pre-existing data specific to each user before you could proceed. Nascent social networks couldn't pull this off.
This also seems to be gameable. Suppose you have blue and green camps as described in the linked paper. And if content gets ranked high when it gets approval from both blue and green users then one of the camps may decide to promote their opinion by purposefully negatively engaging with the opposite content in order to bury it.
This seems no different from "popularity based" ranking mechanisms (e.g. Reddit) where the downvote functionality can be used to suppress other content.
Maybe the assumption is that both camps will be abusing the negative interactions? But you can always abuse more.
