An API could allow devs to create plugins for existing plateforms
For example a comments plugin (for wp, drupal, etc.)
For example, a wp pluging:
A blog post is declared as a position by the author, then users can declare their comments as supporting or not (rating could also be allowed), and the result can be (moderated and) displayed directly on the blog page as a 'visual synthesis' of the debate. Post after post, blog communities could build a huge argument maps, exploring several positions.