Oh this explains so much. I've been raised in the optics that one should always share information in order to make the world better, didn't even think there were other reasons to, like, talk in public.

Since you’re not aware, a very common reason to talk in public is to gain something from one’s talking. The situation at hand looks a lot like that, and in particular gaining something at the expense of someone else in this case. If every ShowHN ended up directing everyone to an alternative project, no one would bother making Show HNs. Hence why it’s questionable about whether the top comment makes the world a better place, etc. That’s also why someone not apparently related to the library at hand could make the same comment without it being negatively received because they don’t appear to have anything to gain from it. I would instead encourage the poster to make their own Show HN the next day rather than hijacking an existing Show HN.