I know it sounds like reinventing the wheel. But imagine a situation where we have a series of posts covering a particular topic and a group discussing that same topic. Each blog post is like a long update about that topic and thus I think it would be useful to have the activity stream discussing that same topic at the bottom of each article. Another option would be to sync the comments from those posts so whatever is written on that post goes to a specific group and not the general activity stream. Does this make sense?