I've tried to create a test commentary using a sample from the post http://community.logos.com/forums/t/36303.aspx that was linked from the PBB Wiki page. I marked it as "Bible Commentary". I also tried the "Commentary" type.
The commentary shows up fine as a parallel resource when I am in another commentary. It shows up if I search for type:commentary. However, it never shows up in the passage guide, even though there are milestones in it. The sample from the post has commentary on the first few verses of John 1. But opening the passage guide for these verses doesn't bring it up.
I tried some of my own document attempts as well without success. It just won't show up in the passage guide. I even waited after indexing was done in case that had something to do with it, but that made no difference.
Is this supposed to work? If so, what is the trick? Do you need to use more than just milestones? Do you have to use them in a certain way?