Undeadly has an article up about recent work on mandoc in a mini-hackathon.  It’s mentioned in context with OpenBSD in the article, but mandoc is also present in DragonFly, and is a potential groff replacement.  (And I think groff is the last item in base requiring C++?  I may be wrong.)  Plus, as I’ve said before, I like mandoc’s output.  It would be nice to use that for our online man pages, for instance.