Yes, I've seen defcon presos on this topic. It wouldn't take great lengths to do so for specific users, if desired. Doing so would be relatively trivial.

Proving a negative (i.e. disproving the claim) here is essentially impossible. Yet, without evidence there's simply no reason to make such an assertion.

Personally, I trust HN and doubt they have any such functionality in place. Even so, can @dang or anyone confirm/deny?