Balkanisation, is a geopolitical term, originally used to describe the process of fragmentation or division of a region or state into smaller regions or states that are often hostile or non-cooperative with one another.
Making a reply in a thread does not always mean you're directly and only replying to the person you're replying to -- it can be more than that, it can be a reply that moves the discussion along, and gives off information and insights to anyone who's reading the comment. Seeing as you're a new HN user, I encourage you to give the 'comments guidelines' page a read: http://ycombinator.com/newsguidelines.html