To answer your question for this specific article: dump the url into the twitter search box(there is a lot of activity there and not a lot elsewhere).

Though in general people have selected to have such discussions off site because they want to talk with people within their chosen communities. To facilitate this it is not always in the best interest of the network to invite outsiders into the discussion.

Just look at Twitter for an example of what happens when you don't do anything to insulate communities from outsiders. If you post an article to have a conversation with people in your network, an influx of outside voices can just show up and make that extremely difficult or unpleasant.