Well, I can't find the spec, but I found what Nathaniel Borenstein told me:
From: Nathaniel Borenstein <nsb(_at_)nsb(_dot_)fv(_dot_)com>
Subject: Re: Images within Text
Date: Fri, 5 May 1995 12:56:09 -0400 (EDT)
.... it's a design decision in MIME. One of the main reasons why the multipart
boundary is defined to INCLUDE the CRLF that leads into it is precisely to
enable this sort of situation. That is, the CRLF before the boundary is a part
of the boundary, not a part of the preceding part, according to the MIME spec.
--------------
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