I built this functionality into a Safari and Chrome extension, that also pairs nicely with the alternative interface I built:
http://hckrnews.com/about.html
Now the question is: why didn't your original announcement (http://news.ycombinator.com/item?id=1552545) ever make the front page? It looks like a nice interface that you put a lot of work into and would be useful to many people...
Hi. Talking about this topic, there is SmartPeople (http://nasr.ath.cx) which lets you subscribe to HN users and threads. You'll then receive any new comment made by any user, by e-mail. The same for the new comments made on a particular thread.