Bundle.signature, although listed as not part of the normative, does cause distraction. Seems it would be better to remove it completely, or move it into an extension. Specifically the purpose of the signature is unclear even if it is not normative. The definition given can be satisfied far more completely through a Provenance resource. A Provenance resource can be brought into a Bundle at any time.

Note that the concept of a signature is more broad than the description of the Bundle.signature element. It includes both electronic, and digital signatures. Thus the definition given is not keeping up with the definition of the datatype Signature.