Reminds me of RTF
Anything from Microsoft should be treated as lies until independent, detailed evidence shows otherwise. Microsoft do not merely do their own thing or write non-compliant web browsers, they have a history of obsfucation, terminating support, vapourware, incomplete documentation and buggy implementations. Withdrawing OpenGL support, terminating DCOM on Unix mid-development, trying to sabotague Java, sabotaguing SAMBA interoperability, killing Pen Windows with vapouware, inadequate RTF documentation, very buggy Visual C++, plain awful ADO, dubious support for ODF... The list goes on and on. And this is the non-Web stuff.
I'm sure others will describe horror stories about Microsoft's attitude to Web standards. Microsoft have shown themselves to be untrustworthy at all levels, especially when developing with their stuff. There is no reason to believe they've changed.