> With the old reddit code, however, you could go to [...] and see a comment view of the entire subreddit.
Depending on the newsreader, you could essentially get the same thing by having the thread with the most recent comment move to the to of the thread list. Then, expanding the thread would show new comments in bold font to distinguish then from ones you've already read or previously downloaded.
Being able to see new posts is something that's lacking in reddit and HN (though reddit does provide this feature on subs you moderate or have reddit gold).