I garbled this the first time; here it is again...
I suppose it may be too complex for people to worry about now, but it always
struck me that in the secure mail / MIME world, what you needed was some sort
of "window" MIME type. If you want to quote something in such a way that the
recipient can veryify the signature on what you are quoting, then you need to
forward the entire signed object and have some way via a "window" MIME object
to reference it and say what part you are quoting.
We actually have this already, more or less -- we have ways of including
material pointed to by a URL in a message and URLs that can be used to refer to
a particular message part.
Specifically, we have the URL access-type for message/external-body. We also
have the ability to incorporate material from a URL directly into text/html
parts. And we have URLs that let you reference either a message (mid) or a part
of a message (cid).
Now,I don't know if the mid or cid URLs forms support any sort of fragment
reference. But it would be easy to add this concept (for text at least) if
they do not.
Implementation of all this is another matter, of course. But the necessary
infrastructure is for the most part already in place.
Ned