But to prevent reposting, the poster -- who doubtless missed the original posting -- would have to search somehow for previous HN posts about the URL. But there is no search facility on HN. You can't blame the poster.
Stating that there is no search box on HN is a.) incorrect and therefore b.) adding nothing to the discussion - so it seems to fit the criteria for downvoting.
Downvotes don't have to indicate "I'm punishing this user", they can simply be "this comment is low-value".
