There's a number of places where COSE requirements are unnecessary restated, referenced, repeated. I think they can be removed and the document would be shorter and more clear. COSE-HPKE doesn't change these characteristics of COSE. When they are restated, there's the risk of restating them wrong or leading the reader to think there's something different when there isn't.
All discussion of CBOR tags can be removed
All discussion of detached vs inline payload can be removed
The CDDL for a COSE_SIgn1 can be removed (sufficient to say that HPKE-base provides no auth)
There's some restatement on how Enc_structure works. It is exactly the same as COSE, right? It really needs to be.
There's a number of places where COSE requirements are unnecessary restated, referenced, repeated. I think they can be removed and the document would be shorter and more clear. COSE-HPKE doesn't change these characteristics of COSE. When they are restated, there's the risk of restating them wrong or leading the reader to think there's something different when there isn't.