"Wait, this code is hard to understand and requires deep domain knowledge. Better nitpick the code style instead. Also, bikesheds should clearly be orange. Green is way too fishy."
Sorry you don't see that.
IMHO, of course.
* no variable-length arrays
* no qualifiers in parameter array declarators (`int x[static 10]`, etc.)
* no `restrict` keyword
* no compound literals
* no designated initializers
There's probably more.
On the web you'll find the same quote copy & pasted over and over saying that support for compound literals and designated initializers was supposedly added in VS2013, but it does not appear to be true. Either that, or I haven't found the hidden switch to enable it. By the way, C code still needs to be compiled as C++ to get anything beyond C89 to work, which should give you a clue as to how serious Microsoft is about C99.
What's true though is that stdbool.h was added. It's a start, I guess...