In my ideal world, there would be such a link between the RSS feeds and PM that they'd always be within a few minutes of up-to-date, if not actually always up-to-date. And there'd be a link in the header of the html code which Firefox could use to find out about the RSS feed.
In my slightly less ideal world, we'd just get the link in the html code to this RSS feed (the one for the current node only - whatever that current node is, although some supernodes may not need it - such as the comment on node. This would still require a bit of work from the PM developers, although I would hope not much. Something like:
<link rel="alternate" title="PerlMonks RSS" href="http://prlmnks.org
+/rss/$nodeid.xml" type="application/rss+xml" />
would need to be added to the header
In my real-as-in-now world, I'd like to express my appreciation of such a service! I just need to figure out how to get this somewhat automated :-)