We currently have a community using a Mailman mailing list which is open for posting without having subscribed/registered on the list. These posts are held for moderation in Mailman through this setting:
generic_nonmember_action = Hold
and the moderation interface allows granted senders to be automatically added to a “blessed” list to avoid further moderation:
accept_these_nonmembers = ...
You could say that the moderator performs a “light-weight” registration process for the user.
May a similar process be configured in Discourse? The main driver is to have zero setup for users wanting to send their first post. It would assume posting by email and it would be fine with an auto-reply that requires a confirmation link to be clicked before the post is accepted (into moderation or directly to list). Suitable defaults could be set for users that are auto-registered in this way.