IANAL but that is not the impression I get from reading your terms and conditions.

> Except as expressly provided in these Terms of Use, no part of the Site and no Content or Marks may be copied, reproduced, aggregated, republished, uploaded, posted, publicly displayed, encoded, translated, transmitted, distributed, sold, licensed, or otherwise exploited for any commercial purpose whatsoever, without our express prior written permission.

A comment on HN is not "expresly provided in these Terms of Use" and don't think would constitute "express prior written permission." If you want to let people use it in their streams you might want to update the language there.