Ask PG/HN: Why does the number of previous comments count in comment ranking?

I'm trying to figure out how I can be a better member of the community (thereby, presumably, gaining more karma), and looking through my old threads I noticed that often, even when my comments have the most points on a story, and even when my karma isn't any lower than the other people commenting, my comments are at the bottom of the page. The only thing I can find that could cause this is that I've posted 22 comments while others have consistently posted more. My "average karma" is nil, and I assume this means I haven't posted enough to begin its tabulation, and I remember recently PG said something about revamping comment ranking to include this statistic.

I can understand a sort of "probation period," in which new users are expected to spit out solely inane things, but I have a number as low as 22 because I generally only comment when I feel my comment seriously adds to the discussion, and (I feel) not because of a lack of familiarity with the community. On SearchYC, my average comment score is 4.86. I assume that I'm not being singled out, and that other people are in this situation as well. So, is there an explanation I'm missing here?