I did an OPS-DIR review of Manufacturer Usage Description Specification < draft-ietf-opsawg-mud >
The specification is well written and clear (I also agree with Robert Spark's nits).

One suggestion about document organization: I would either move the discussion of what should be done if the MUD controller can not retrieve the MUD file for some reason or another out of the security considerations section to after section 1.9 or at least include a forward pointer to the discussion.