I think it's worth noting that most of the articles submitted to HN have no comments on them, meaning if those pages without comments were indexed by google and

I think it's worth noting that most of the articles submitted to HN have no comments on them, meaning if those pages without comments were indexed by google and included in their measure of our reading level, there would be many pages consisting of only the words: "flag, 1 point by xxxx, no comments, Hacker News, new, threads..." etc etc. So maybe that has some influence on google's calculation.