Multiple doc formats
"Word has just Doc and Docx as native formats as far as I know - and still supports saving in both. As Docx is now extensible, I doubt you will see a new format anytime soon....."
Yeah, that is mistaken. .doc is just whatever format Word happened to use at the moment. It had one format for Word for DOS, one for Word <6, one for Word 6, one for Word 7 and 95, then for Word 97 they switched to the 97-2003 format. Then they switched to docx.
I'll ignore the DOS format. Word 5.1 for Mac came out in 1992, so 4 incompatible file formats in 5 years. They then managed 10 years of compatibility, although 2003 supported docx it was not default until Office 2007.
Anyway... if Microsoft's true interest were compatibility (rather than sticking it to Google), they should simply take google's properties off their (in)compatibility list since this is breaking rendering.