The email.utils.formataddr function is used to encode a name-address 2-tuple for use as an email message. If the name contains a non-ASCII character it needs to be encoded. This happens correctly in Python 3.3.2, but incorrectly in Python 2.7.5. Ideally Python 2 would acquire the Python 3 behaviour, as this should make porting easier.

In the following Python 3.3.2 example the name is encoded because of the non-ASCII ☢ character:
>>> import email.utils
>>> name = 'Me ☢'
>>> addr = 'mpj17@onlinegroups.net'
>>> email.utils.formataddr((name, addr))
'=?utf-8?b?TWUg4pii?= <mpj17@onlinegroups.net>'

In Python 2.7.5 the same name is incorrectly left unaltered:
>>> import email.utils
>>> name = u'Me ☢'
>>> addr = 'mpj17@onlinegroups.net'
>>> email.utils.formataddr((name, addr))
u'Me \u2622 <mpj17@onlinegroups.net>'

However, calling the email.header.Header.encode method works around this issue in Python 2:
>>> import email.utils
>>> import email.header
>>> name = u'Me ☢'
>>> addr = 'mpj17@onlinegroups.net'
>>> h = email.header.Header(name)
>>> email.utils.formataddr((h.encode(), addr))
'=?utf-8?b?TWUg4pii?= <mpj17@onlinegroups.net>'

The example code immediately above also works in Python 3; it is the current work-around in GroupServer. However, ideally instances of Unicode objects passed to email.utils.formataddr will work the same in both Python 2 and Python 3.

At the time we introduced this behavior in python3, it was considered an enhancement and thus not suitable for backporting.  So you'd have to advocate for backporting it on python-dev.  My guess is it won't be approved, especially since there are significant other differences in the python2 vs python3 email packages (eg: BytesParser/BytesGenerator).

I care enough to lodge an issue, but I lack the conviction in order to belabour the point in python-dev! I'll mark this issue as closed.

Hopefully the work-around in my original post will help others :)

Well, the "work around" was how you always had to do it in python2.  So this is just a bit you can't port to the easier Python3 interface until you can drop python2 support.