HN doesn't support full Markdown. :(
I was always partial to the variants that could do citations well. They would automatically link-ify items postfixed by [1] etc with the link included at the citation at the bottom. I implemented a customer facig newsletter system at one job using that, where it automatically made the emails multipart when markdown was submitted, with the text part being raw Markdown. When using citations, it's still very readable.
Thanks for causing me to look again (I used babelmark[1] to check what versions supported it and noticed all of them do, including Markdown.pl). I dislike putting out wrong information. :/
1: http://johnmacfarlane.net/babelmark2/?text=%5Btext%5D(url)