Hi,

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


nits:

COMMENT A)

"""
2.1.  Rules

   The following rules apply within the Nickname profile of the PRECIS
   FreeformClass.
"""

I might be helpful to add the reference to RFC7564 after the FreeformClass
as you did in section 2.2. Another way could also to assume in the
introduction the reader is familiar with RFC7564. I also agree RFC7564 is
mentioned in the terminology section.

COMMENT B)

"""
 4.  Normalization Rule: Apply Unicode Normalization Form KC.  Because
"""

Two unexpected white spaces. Can be fixed by rfc-editor

COMMENT C)

"""
6.  Security Considerations

6.3.  Visually Similar Characters
"""

Maybe a reference to the example section with the names 5/7 or 6/7 can
illustrate that the current profile does not prevent visually similar
characters.