That's a good point, I hadn't thought of that. Discourse (which I think is what's behind the Juno forum, and the Atom discussion group) seems to do: Discourse Mailing list mode <http://discourse.mcneel.com/t/mailing-list-mode-for-discourse/5763> Discourse reply via email <https://meta.discourse.org/t/new-reply-via-email-support/7764>
But I've never used mailing lists properly, so I can't say whether this would be satisfactory to those who do.
