A few nits:
In the informative note at the end of sec 3.1, suggest untangling the last 
two sentences to :
  For this reason signers SHOULD NOT reuse selectors with new keys, and
  SHOULD assign a new selector to each new signing key.
In 3.2, just above the description of h= there's an extra l in 
"address-literall"
In second pp of 3.9, third line, "hnamas" should be "has"
R's,
John
 smime.p7s
smime.p7s
Description: S/MIME Cryptographic Signature
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