On the note of the rich getting richer, it isn't only when someone arrives in a thread. Average comment score is also a big factor. The way the algorithm works is that late arriving commenters with high average comments scores can often jump ahead of older comments from users with lower comment scores.

Once example, I created a new HN account a little over a year ago to switch from a slightly unprofessional name to my current one. Some of my early comments got upvoted a decent amount giving me a higher comment score. That higher comment score led to appearing closer to the top of comment chains. That in turn resulted in more visibility and again more upvotes. I don't think the quality of comments is any different between the two accounts, but the comment score on this one is 2.5x higher simply because I started out with a lucky advantage.

I am not sure if people will view this as a problem, but I certainly wasn't aware of how big advantage having a high average comment score was until I had one.