HN is not a representative sample of normal people and has a long understood inability to recognize satire, or even just particularly strong sarcasm. HN not getting a joke is not evidence of it being a bad joke.
I've never seen an online community fail to grasp sarcasm as badly as HN. I deliberately make one out of 50 posts ultra-sarcastic (to the point where no normal person could possibly believe I'd hold whatever view I wrote), and they always, always go straight to -4.