Hacker News isn't even listed on search engines because it disallows Googlebot.
User-Agent: *
Disallow: /x?
Disallow: /vote?
Disallow: /reply?
Disallow: /submitted?
Disallow: /submitlink?
Disallow: /threads?
Crawl-delay: 30
Links in comments are marked nofollow but submissions are not.https://news.ycombinator.com/robots.txt
shows no such thing...
The file from January 2013 appears just as permissive:
http://web.archive.org/web/20130109093744/http://news.ycombi...