In addition to "Internet points" mentioned above - influence operations, both from nation states (e.g. the PRC 50 Cent Party, and probably the dozen most powerful nations in general), and from gray/black-market marketing companies.

Influence is valuable, and HN is a place that people who are aware of it trust highly.

(AI generation of random comments helps build "trustworthy" accounts that can then be activated when a relevant issue comes up)

[1] https://en.wikipedia.org/wiki/50_Cent_Party