I simply perform a text search (using Postgres' text search functions) on the backlinks, rank them, and sum their scores. This is meant as a very temporary ranking method before I implement something like an actual PagRank.
I say leave pagerank out of it, otherwise desperate people will link across these small communities like crazy to inflate their discoverability.
I think the most fair[1] thing you could do is a random ranking, and print the seed at the top in case anyone wants to reproduce their results.
1: https://en.wikipedia.org/wiki/Random_ballot