That particular blog author displays special content if the referrer is HN. It's embarrassingly juvenile for someone that must be in their 50s by now.
Having had that a few times, and recently relaxing Firefox's referer policy for some other site compatibility which had avoided it before, I came to this workaround with uBlock Origin:
Hopefully documenting it doesn't perpetuate the arms race.
Oh sorry, I did not know that was the guy who hates being linked to from HN. Copy the link manually to read it if you still care to learn what he wrote.