Anyone could (in a technical sense) scrape HN or access the data through the API and do whatever they want with it. It's unclear to me whether the license granted to HN by your use of the site gives someone doing so license to your comments (I suspect not but IANAL) but the general argument here is that this would fall under fair use. Certainly that seems the case if they didn't display the dataset itself. I'm not sure how it would fair though given they are displaying the content.
