The OPML generator revealed an interesting use case -- tracking the blogosphere's opinion on specific topics or products through comment feeds.  However, this is typically not what folks want to add to their normal subscription list.  I've refined control of the return of comment feeds and added the ability to include/exclude category/tag feeds.

I've also added the ability to nest exported OPML rows in a top level category. This facilitates grouping in some news readers.  Enjoy your OPML