Two more points…
1) An email-reponse route will make intelligent reponses difficult if the post you’re responding to contained embedded media, or even uoloaded media…That’s one reason not to pursue it so carefully.
2) Back to Jon’s original question. It’s not so clear to me that these are distinct types of software – both are operating by hoovering up the best features of the other. For example, WordPress — whihc started out just to enable blogging — is now used by some for CMS.
What seems essential is that we have an online community, which has an open extensive and supportive infrastructure and could be more integrated than a set of mailing lists with a common log-on….