So what we are reconciling here is:   "The meaning and structure of extension values under an IRI key are defined by the person who coined the IRI, who SHOULD be the owner of the IRI, or have permission from the owner".  I think the definition of IRI takes care of most of it, but that there should be somebody in charge of it.  I don't want to get into ownership, so would rather just say there is a controller.  Whether the controller owns it is beyond the scope of this document.  Given that this is just a SHOULD and we don't define these permission sets.  If we want to broadly apply this requirement of extension IRIs to all IRIs, then we can move it to 5.4, but for 1.0.1, I think it stays here and talks only about extension IRIs.  Open for discussion on it, though!