Are you a moron? Who would you sue - the username?
All that said, the point apparently wooshed a few miles above your head.
I posted a link to someone else's legal disclaimer as an example of how legal advisory services protect themselves. They used it to try and paraphrase my own comment back to me, unsuccessfully.
You could subpoena HN but it would display a startling lack of understanding about ISPs, legal process, HN and the Internet.
One, a subpoena has to be delivered in person...