If they actually, honestly didn't want their inane spam posted on HN, they could easily achieve that simply by returning a non-response or redirect or error for

If they actually, honestly didn't want their inane spam posted on HN, they could easily achieve that simply by returning a non-response or redirect or error for any requests with a HN referer header. They do not do that because they actually do want to continue getting traffic from the inexplicable portion of HN that insists on posting their crap all the time.