Rob, thanks for the question.
The integration with ActiveForums currently provides the ability to have Comments on an article go into a thread in the forum. If an article is configured for Comments and the parent category has a default forum defined, when the first comment is added to the article a new thread is created in that predefined forum.
The subject of the thread is titled with the name of the article, the text of the original post is the description/abstract of the article, and then a link is inserted to the actual article. The comment that was added by a user then becomes a reply to this original post.
This way only articles that have comments get created in the forum, not every article entered on the site.
From there, anytime someone wants to comment on an article it takes them directly to the thread in the forum, to which they can read other comments and reply.
The ratings for articles are still held within Engage: Publish's default ratings, not within AF.
Does that help?