I've posted the results of the strawpoll on the proper usage of @debian.org email addresses to the debian-project list. It seems most people think it is alright to use them in Debian or Free Software related matters. Most also did not approve to use @debian.org as a general-purpose email address or for stuff completely unrelated to the Debian project and its principles.
It must now be discussed what to draw from the results and whether to update the DMUP or rather amend the Developer's Reference to document best practise on @debian.org usage.