I'm also interested in this :-) I had a look here: http://www.ycombinator.com/legal/, and found this:

> "By uploading any User Content you hereby grant and will grant Y Combinator and its affiliated companies a nonexclusive, worldwide, royalty free, fully paid up, transferable, sublicensable, perpetual, irrevocable license to copy, display, upload, perform, distribute, store, modify and otherwise use your User Content for any Y Combinator-related purpose in any form, medium or technology now known or later developed. However, please review the Applications Privacy Policy located at https://www.ycombinator.com/apply/privacy, for more information on how we treat information included in applications submitted to us."

> "You acknowledge and agree that any questions, comments, suggestions, ideas, feedback or other information about the Site (“Submissions”) provided by you to Y Combinator are non-confidential and Y Combinator will be entitled to the unrestricted use and dissemination of these Submissions for any purpose, without acknowledgment or compensation to you."

That's the text related to people's comments that I found. It grants permissions to Y Combinator, and they don't grant the rights they get, to anyone else. So, as far as I can tell, you're not allowed to do that. (I'm not a lawyer; this is not legal advice. (Does one need to say that also if not in the US? :- P ))

What do you think?

Instead, I'm thinking about dynamically check for URLs at HN, and then auto-post a comment in an embedded commenting system I'm developing (See my profile :- )), that links to the discussion at HN. And maybe manually reply to the comment, with a brief summary of the HN discussion. And the same, for discussions at Reddit, maybe Mastodon, etc.