I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the
IESG. These comments were written primarily for the benefit of the
security area directors. Document editors and WG chairs should treat
these comments just like any other last call comments.

The summary of the review is Ready.

The document extends the "CDDL Control Operators" registry with 14
new entries, control operators. The document is well written. The
Security Considerations section refers to RFC 8610 and RFC 4648. 
I agree that these documents provide the main considerations 
relevant for this spec. I believe the document is ready.