I think I understand the issue now. I will write something
in the informational document to be produced in conjunction
with the standard, draft-ietf-mhtml-info-09.txt.

Question: What should be done?

(1) Should the e-mailer of the recipient be set to use 9 pt
    as a base font for plain text messages, but 12 pt as a base
    font for HTML-formatted messages?

(2) Or should the base font size for the sender be
    different when reading and writing HTML?

(3) Or should the base font size for the sender be
    different when writing web pages in HTML than when writing
    e-mail in HTML?

Alternative (3) does not seem right, since we have
intentionally designed MHTML to make it easy to have the
identical document sent by e-mail and provided on the web.
Alternative (2) does also not seem nice, since a person
should be able to edit HTML in WYSIWYG showing it as it
will look like when seen by recipients. So (1) seems to me
to be the right solution. If a person wants 12 pt as a base
font for reading HTML pages, why would not that person want
the same font when reading HTML-formatted e-mail?
------------------------------------------------------------------------
Jacob Palme <[log in to unmask]> (Stockholm University and KTH)
for more info see URL: http://www.dsv.su.se/~jpalme
Between 26-31 June use phone No. +46-8-664 77 48 not +46-8-16 16 67