If the certificate contains only one Node-ID then only the certificate is use in the hash, if not then the hash is calculate fom both the certificate and the Node-ID.  The text was an attempt to not contradict the defintiion of SignerIdentityValue.

This was in response to Peter St Andre comment: "In Section 5.3.4, what exactly is "the identity used to form the signature"? It appears to be a Node-ID (or a hash thereof), but it would be good to make that clear in the definition (e.g., could it also be a Resource-ID)?"