"... The feed is in Atom format. It works in Safari, but not in Firefox. ..."
The reason why is you need a link tag per entry. For example:
feed
...
entry
title
id
updated
link <link href='http://foobar.com/permalink'/>
summary
content
the link bit was what I was missing so firefox goes to retrieve the link, finding it's not there fails. I just spent some time today fixing this myself.
"... Feedvalidator tells me that the date does not follow RFC-3339 ..."
I've got the same bug on my todo list. For some reason the date string format works ok but doesn't render "T" & "Z"'s. Also liked the disqus integration which I have yet to work out. Have you got any idea how much more data per post the discussion adds?
The feed is in Atom format. It works in Safari, but not in Firefox.
Feedvalidator tells me that the date does not follow RFC-3339. I'll fix that.