I wonder if this data might be more interesting on the bottom 100 users with a longevity > 2 years. And of course it would be interesting to see the differences between the top 100 HN users and the top 100 Reddit users. That might provide some insight into the echo chamber effect.
I agree with that, one interesting question though is can you use data like this to characterize the echos. If so, then one could point it at an arbitrary forum, score the top 100 posters, and pull out a 'flavor' for the forum. That would be kind of neat.
