[ietf-dkim] Nits with section 3 Operation Overview

[Arvel Hathcock]

Just one suggestion.    I would rewrite the second sentence like this:

  "This practice would be used by those domains who wish to emphasize 
security over deliverability of their messages."

and leave out the bit about what we think the typical use case for this 
might be.  In fact, since none of the other practice options provide a 
rational behind why they would be used I don't see the need to do so 
here either in which case the entire sentence could be removed.  Or 
perhaps a NON-NORMATIVE DISCUSSION section could be added where the 
possible use cases and cautions could be given.

More coming
    
Arvel