If you didn't notice, in recent releases the Digg and Reddit social beacons were missing. They were removed some time ago to make space for a better method of discovering comments. I had released a stand-alone app FindComments few weeks ago. It uses ContextVoice to find comments from all sources (Twitter, Digg, Reddit, and many more). In v2.0.6 that app is integrated with ReaderScope. You will see a new icon on the action panel, which you can tap to find comments on the current news item from all over the web.
Try it on some popular news stories from Slashdot or XKCD to see how it works.