The beautifier isn't enabled for ANSI C. If I recall correctly, this is for historical reasons. Unless you go pre-ANSI, and pull out some K & R syntax, I think the C/C++ beautifier can handle it at this point. We have C89 projects as unit tests for that beautifier.
But it's not something you'd be able to enable on your end with just some tweaks. The only way you can run the C/C++ beautifier on the ANSI C file is to change the mode to C/++.
