RE: Delivery Receipt, NRR and MSG/CPPA/BPSS (mis-)alignment and thelayering mishmash (was jumbled into: reliable messaging - hop by hop)

Yes, absolutely, everything the MSH does is at the behest of an application. The sending MSH performs/requests NRR when receiving a signal from the application, in conjunction with a file to be sent.  The receiving MSH actually does NRR when receiving a deliveryReceiptRequested=Signed.  David Fischer Drummond Group.