I’ve seen it happen when I’ve flagged stories so either there is a vast conspiracy of moderators that receive pages when I flag things so they can downrank… or maybe dang isn’t lying about something that should be super obvious as a community self policing mechanism.
It's discussed in the link, and elsewhere [1]. Some mod actions on HN are transparent, some are not. You should not assume that, just because you see marks of some form of moderation, that you can see them all.
Undisclosed content moderation is like directly modifying your production database. It's faster, but always more troublesome. Nobody else knows what changed or why, etc.
[1] >>36435312
[1] https://www.supremecourt.gov/docket/docketfiles/html/public/...
[2] https://www.supremecourt.gov/docket/docketfiles/html/public/...
[3] https://www.supremecourt.gov/docket/docketfiles/html/public/...