Neither I found CFWS in rfc2231.  In addition, rfc 2045 (Introduction) says that Content-Disposition —where filename is defined— cannot include comments.  However, Content-Type can include RFC 822 comments, so the filename should be de-commented in case it is inferred from the name parameter there.

I'm rather new to Python, and sticking to version 2 because of the packages I work with.  I see Python3's email has a much more robust design.  Does this mean Python2 cannot get fixed?

I attach a de_comment() function, copied from the one I mentioned this morning.  The rest of the file shows its intended use.  (Oops, it removes comments even from where they are not supposed to be allowed ;-)
Having that kind of functionality in email.utils would make it easier to read Message's, no?