After long and arduous attempts, resulting in some code that's actually quite nice and could be repurposed elsewhere, it turns out that the BC data is much less predictable than that in the PEI files, and not really amenable to automated approaches to merging paragraphs; everything from triple-asterisk dividers to headings to one-word labels ("Prayers") appears in paragraph tags, so there's no practical way to merge paras which are split over milestone boundaries. Oh well, we gave it a good shot. GL and ST will have to handle this manually. Fixed some other bugs in the process, though, and what is there now still works.