I think I misunderstood you about halfway. The node/counter-node idea on E2 is as much a feature of the community as it is technical. It's pretty simple to have community node editing; there's a Wiki nodeball that we even use here on Perl Monks.

The engine itself just provides database persistence, a behavior system, users, permissions, display customization, linking semantics, and an API. Anything else is up to the users. :)