That's a fair question. If the website was accessible, we might be able to learn the answer:) From the perspective of HN, the usefulness of the linked content is far less important than a person's ability to participate in the discussion. The product might not be useful for a blind user, but there is no reason for the content that explains it to be inaccessible.

Not everyone who uses a screenreader is completely blind. Vision impairment is quite a wide and varying spectrum. Also the person viewing the site might not be the person who will be using the software. Perhaps it's not applicable here, but imagine a scenario where the person responsible for purchasing the software uses a screenreader.