@julian @erincandescent @evan @silverpill Let me put it this way: the latter half of FEP-7888 can be summarized as "reifying context as an object, and specifically a Collection". If you *just* want the grouping, then it could be an arbitrary opaque IRI. But what you gain by reifying the context as an object is specifically the ability to give it metadata properties. Particularly things like `attributedTo` or `audience`. Maybe even `followers` or `outbox`. An opaque IRI cannot do this.