I said many years ago that it would be interesting to rate posts not in some pseudo-objective good-bad way but in terms of agreement or not, and that you could then modulate the ordering of posts on a per-user basis by proximity to the preferences of people you had expressed preferences about.

This was dismissed as overly complex for arc, but I really would like to see the unfiltered graph of HN's social network to study the various voting rings and social subgroups.