Kicking this one uphill from a comment to an actual post, since it may clarify matters for any other readers, too, with questions in this area:
Okay. Let me try this again.
All minds, as defined in the ‘verse, are Minskian societies of mind, masses of independently running agents on a shared substrate, from which consciousness, volition, and all other mental properties emerge. (“The Country of the Mind” in Greg Bear’s Queen of Angels would be a good symbolic representation.)
This, for example, is how technologies like the gnostic overlay work; by patching some new voices into the chorus.
The Transcendent soul-shard (hence its technical name, logos bridge) serves as a bridge between two societies of mind, carrying messages back and forth, allowing both the participation of the constitutional’s agents in the Transcend’s mentality and the participation of some of the Transcend’s agents in the constitutional’s. This blurs the strict lines of identity, arguably, but it’s not a complete subsumption of identity such as occurs on joining a Fusion; rather, every time a new constitutional Transcends, both they and It become somewhat different people in various ways, wedded together most intimately, but they don’t achieve identity of identity.
(Incidentally, as I think I mentioned in a 2012 piece, the main reason the Transcend keeps an economy and a governance around, is that they work. Sure, technically, you could replace market coordination with coordination mediated through coadjutors and Transcendent oversouls, but because of that mathematical theorem that demonstrates that even a hypothetical Omniscient Calculator could only at best equal the performance of a free market, not beat it, you’d have nothing to gain except wasted cycles and the lack of a convenient interface to the rest of the universe. Similar logic applies to various other applications.
Basically, you don’t send an oversoul to do a simpler instrumentality’s job.)