Good to know. In that case, probably the biggest distinction between HuffPo and HN is that HuffPo displays the content on their own site. For some writers, that might be a plus. For others, it might be a minus.
I've heard some professional writers say you should rarely or ever publish anything (e.g. a blog post) without remuneration. Not because it's wrong to do so, but because they consider it bad business. If they're right, I don't know if that should affect our judgment of a publisher who actively solicits unpaid submissions. Maybe the writers are undervaluing themselves, but then maybe the publisher isn't to blame for that.