I suggest to change the title from "Party identifiers" to "Participant Identifier Schemes"
I suggest to change the text
Party identifiers (cac:PartyIdentification/cbc:ID) and party legal registration identifier (cac:PartyLegalEntity/cbc:CompanyID) has an optional scheme identifier attribute (@schemeID). If used, the value shall be chosen from the code list codelist-ICD
to
Participant Identifiers (EndUser/ParticipantID) have a mandatory scheme identifier attribute (@schemeID). It shall be chosen from the EAS Code list.
to
(see also next issue)