Comment 2 for bug 266341

I think you have found the cause. Scrubber also does the
same thing when flattening the message, but now we have a
difficult decision.

If we want to 'fix' Decorate, we now are faced with a
situation where we may be adding a 'format=fixed' header
and/or footer to a 'format=flowed' message body. This
potential incompatability may require us to 'wrap' the
message and add the header/footer as separate parts in this
case. This will undoubtedly raise additional complaints.

In the case of Scrubber, this may lead us to scrub the
actual message body part - not a good thing.

I may be over-reacting here. It may turn out that it is OK
to render the header/footer/scrubber messages as
'format=flowed'. Although I can contrive a footer for
example (by putting trailing spaces on intermediate lines)
that will be munged by rendering as 'format=flowed', this
may not be a problem in practice, and Decorate could always
be made to strip the spaces.

There are also potentially issues with stripping of leading
spaces because of the assumption that they are 'stuffed'. I
don't know how big an issue this is in practice.

Note, if we do preserve 'format=' we also need to preserve
'delsp='.