Probably because they, unlike you, are able to read comment datestamps?
EDIT: this is fascinating. On web, their comment shows as 1 hour ago. But on my mobile app, their comment shows as 3 days ago. Looks like the HN mods second-chanced this article, and it edited all the old comment timestamps as a result?
Gotta be some bug because I've seen a thread 4 days ago on mobile that was yesterday shown as new on desktop with comments that I clearly read already dated also as new, posted within hour.
Booting from an USB Drive understanding a few menu options is in fact what I would call "basic tech literacy".