--On Tuesday, September 10, 2013 08:09 +1200 Brian E Carpenter
<brian(_dot_)e(_dot_)carpenter(_at_)gmail(_dot_)com> wrote:
...
True story: Last Saturday evening I was sitting waiting for a
piano recital to start, when I overheard the person sitting
behind me (who I happen to know is a retired chemistry
professor) say to his companion "Email is funny, you know -
I've just discovered that when you forward or reply to a
message, you can just change the other person's text by typing
over it! You'd have thought they would make that impossible."
There is another interesting detail about this in addition to
the part of it addressed by the brothers Crocker.
When MIME was designed, there were a number of implicit
assumptions to the effect that, if an original message was
included in a reply or a message was forwarded, the original
would be a separate body part from the reply or forwarding
introduction. Structurally, that arrangement not only would
have preserved per-body-part signatures but would have largely
avoided a number of annoyances that have caught up with us such
as an incoming message that uses different charset values than
the replying or forwarding user is set up to support.
Obviously, that would not help with replies interleaved with the
original text, but that is a somewhat different problem
(although it might take a bit of effort to explain the reasons
to your chemistry professor). When things are interleaved,
preventing charset conflicts, modification of quoted text, and
other problems is pretty much impossible, at least, as Dave more
or less points out, if the composing MUA is under the control of
the user rather than being part of a centrally-controlled
environment that can determine what gets typed where.
It didn't work out that way. Indeed, more than 20 years later,
forwarded messages and "reply with original included" ones are
the primary vestiges of the popular pre-MIME techniques for
marking out parts of a message. Perhaps we should have
predicted that better, perhaps not. But the reasons why "make
that impossible" are hard are not just security/ signature or
legacy/installed base issues.
best,
john