" I'm still not really clear how that could work any better than simple anarchy."
Well, with such a basis for further agreement to 'ride' on, business would be easier to conduct. Maybe not, but it seems that having known points of agreement already established through prior examples would make drafting other ancillary agreements easier, and avoid much revision.
And as to the example you provided of a commune, that is a part of the problem with communes. It is a good example of real world issues communes actually face, and people have to decide how to handle. Being authorized to make a decision doesn't make that decision necessarily easy, however.
Regarding extant property, I haven't had my morning coffee yet, so am gonna have to defer that issue.
That is a thorny problem, and I'm pretty sure I alone will not come up with the solution.
Edit: I failed to address the Ubuntu movement you mentioned. This would be another example where knowing what their governance model is would make it easier for me, or you, to decide whether we wanted to participate.
I, like you, am not enamored of a council of elders making decisions for me. Such a hierarchy is less than ideal, and I'm agin' it.