As to the question of argumentation, the list I'm talking about ("wikien-forum" in my proposal) would be specifically biased against argumentation and direct replies to individual points. Most contributions would have to be able to stand on their own: thematically related to the thread, but no quoting, ranting, or kvetching. People who want to have direct discussions would be encouraged to do so, just not on the list.
How does that work? All conversation pretty much falls into two categories - informative and argumentative. Informative takes the form of question and answer, argumentative takes the form of point-counterpoint. Either way involves each email being a reply to a previous email. A dialogue does not consist of a sequence of monologues, and mailing lists are intending for dialogues (or polylogues, or whatever you call multi-way conversations). If people want to post monologues, they can start blogs.