While the envolve plugin is extremely interesting, the HN implementation would probably be far more useful if you scraped the HN username for logged-in users and displayed it. Anonymity seems to kill the utility of chat. For those that wish to participate anonymously, you can always offer the option to opt out.

Using jQuery, this should be trivial:

$(".pagetop").children('a[href*="user?id="]').attr("href").split('=')[1];