Whoops, missed a lot of responses here, sorry about that! Yes, vanilla Pagerank (where the "sites" are accounts and "links" are upvotes) is the first thing tha

Whoops, missed a lot of responses here, sorry about that! Yes, vanilla Pagerank (where the "sites" are accounts and "links" are upvotes) is the first thing that came to my mind, mainly because it's been pretty well battle tested; running it on the comment graph is actually a much simpler problem than running it behind a search engine because you don't need the additional refinements based on search keyword. A comment's Pagerank is, by itself, enough to set an ordering. If that's too much work, though, even a simple vote weighting based on some function of the upvoter's karma would be a decent approximation. Say every user's votes had an impact based on some sigmoid function of their karma (maybe a Gompertz function?), tuned so that the plateau is hit for the top 10% of users or something like that.