I understand that HN tries to be pretty on topic & focused and does not appreciate unrelated comments etc. As such silly jokes etc are generally frowned upon.
However, humor can also be used to get a nontrivial point across and doesn't have to be "empty of content". It seems to me that the same point phrased as a declarative statement vs a joke are received completely differently.
For example,
1. "Tesla is overvalued because of x, y, z."
2. "Just read about x, y, z. Better call my broker and dump some shares."
Sometimes the addition of humor can show just how silly the context is, something that a formal declarative statement cannot.
So, why does HN hate humor?
HN hates lazy comments.
HN hates ugly comments and a lot of humor is both lazy and ugly.
HN intentionally and consciously seeks to keep the signal-to-noise ratio high. Humor tends to harm the signal-to-noise ratio, which further fuels HN pickiness about what kind of humor is acceptable here.
Humor on the internet is inherently challenging because it often relies on voice tone, body language and other cues to signal "This is a joke." On the internet, memes substitute imagery in a way that helps provide visual cues and the formatting here doesn't support communicating in that style, which makes humor even more challenging on HN.
If you are looking for light-hearted snark for some reason, HN is really not the place for that. There are plenty of places to find that and that's just not the purpose of this site.