In a Ars.Technica article:
Portugal's meeting was even more interesting. In what can only be described as a comedic farce, representatives from Microsoft attempted to argue that Sun Microsystems, the creators and supporters of the competing ODF document standard, could not be given a seat at the conference table because there was a lack of chairs. In the debate, representatives brought up many of the standard criticisms of Office Open XML, such as the infamous "AutoSpaceLikeWord95" tags. Microsoft confirmed that such tags would never be included in a new document, and were only there for backwards compatibility with older applications, and had been added only at the request of organizations such as the US Library of Congress and the British Library. Microsoft was also asked why it couldn't simply extend ODF to include its backwards compatibility needs, and the company representative said that the OASIS group "rejected Microsoft's proposals and expelled/excluded the Microsoft representative because the proposed changes would add backward compatibility to legacy documents."
Emphasis mine. I'm speechless... I mean, I really think that Microsoft people would be smarter than this, right? Not enough chairs?
Update: IBM is offering to bring chairs! Thanks Bob!