Now in practice, dath ilani are still mostly human, and therefore way too computationally bounded to aggregate into even a not_too_visibly_incoherent-bounded_approximation of a macroagent.
Conceptually and to second-order, then, Civilization thinks it should be divided into a Private Sphere and a Public Shell. Nearly all the decisions are made locally, but subject to a global structure that contains things like "children may not be used for slave labor"; or "everybody no matter who they are or what they have done retains the absolute right to cryosuspension upon their death"; or the top level (in most places the only level) of the imaginary system of ownership-tags and its contract-specification-language.
The vast supermajority of Civilization's real economic activity takes place within the Private Sphere, supported and contained and constrained and structured by the Public Shell. It's not that activity inside the Private Sphere is uncoordinated. It's that the decision as to how coordinated to be, and who to coordinate with about it, can be left up to each individual, computed locally - so long as they don't kill anybody, or take stuff that doesn't belong to them, or try to raise their own flaming-ass children with a proper conlang and without flaming-ass Baseline contaminating their innocent smol minds.
Conceptually speaking, this division overwhelmingly factorizes the computational problems of the approximated macroagent, and simplifies the vast majority of dath ilan's decision problems immensely. It reduces the mental expense of almost all day-to-day life back to something individual humans can handle. Indeed, dath ilan does not want to become any more of a coordinated macroagent than that! Its prediction markets say things-defined-as-bad will happen according to its aggregate utilityfunction, so dath ilan isn't doing that.
This does however leave some amount of decision-power to the Public Shell. Some words must be spoken in one voice or not at all, and to say nothing is also a choice.
So the question then becomes - how, in practice, does Civilization aggregate its preferences into a macropreference, about the sorts of issues that it metadecides are wise to decide by macropreference at all?