I just searched the net for instances of Format=Flowed; Delsp=Yes and found
quite a few (all from Apple Mail). Almost all ofr the messages were CTE:
quoted-printable.
This rather misses the whole point of the format, doesn't it? RFC2646 says
you SHOULD NOT use quoted-printable.
Besides which, quoted-printable already has a mechanism for soft line
breaks.
As Arnt Gulbrandsen pointed out last year, don't MUAs for CJK already need
to handle quoted-printable, multiple charsets, etc.? Does Format=flowed
really add anything?
For what it's worth, I did find a few Japanese messages with CTE: 7-bit
http://www.egroups.co.jp/message/minnademac/3563?source=1
http://alpha.c.oka-pu.ac.jp/~yokota/gakkai/etc/npdpa02