I got no solution but all I can tell is: you’re not alone ;-)
There are several correspondence related elements (opener, closer, postscript, salute, signed) which impose a (prototypic) structure that not necessarily matches with "real“ correspondence texts. The issue is on the Correspondence SIG’s agenda  but has been deferred because we started with the "easy" header additions .
Am 26.06.2014 um 10:24 schrieb Peter Boot <[log in to unmask]>:
> This seems like a rather basic question, but how do you all deal with salutations that are embedded within the first paragraph of a letter or postcard?
> When the salutation is placed above the text, we use:
> <salute>Dear Freddy</salute>
> <p>How are you?</p>
> But we have a postcard that starts like this:
> Dear Freddy, how are you
> Since salute is not allowed immediately in a paragraph, we could introduce a new element ('opener-inline') to deal with this:
> <p><opener-inline><salute>Dear Freddy</salute></opener-inline>, how are you?</p>
> Or just allow salute within p, which seems the preferable solution to me.
> Similar issues arise in closing salutations, that can also be embedded within regular paragraphs. We have a postscript like this:
> <postscript><p>Mr. Foster came to see me, I am going to
> him tomorrow. <salute>Good bye. Au revoir!</salute></p></postscript>
> where you wouldn't want to move the salute to a fictitious closer.