I'm sure that there are a lot of cases where you could make code look neater and sleeker with this kind of syntax extension, but my thesis -- and this is inherently hard to prove -- is that the uglier code you may have to write in C is nonetheless more robust and maintainable code in the end. A lot of very good software has been written in C, and what I suspect contributes to C's impressive record of robustness is its spare syntax and the fact that there is almost no room for ambiguity and subtle, invisible side effects. What you see is what you get.

Adding simple, inline anonymous functions like these is a fairly modest proposal, of course, and I can't tell you exactly what damage they'd cause. They could turn out harmless. But they are redundant, because C already has a syntax for functions, and that redundancy now forces the programmer to have to make a choice about which syntax to use every time the situation permits them. Reading code becomes a bit more complicated, because there are more kinds of syntactic elements to recognize and know the consequences of. You end up splitting your time between two ways of writing functions, and that works against developing consistent practices and conventions for writing functions.

Is there a trade-off? Probably. It may be too onerous to write some types of code in C, and a little syntactic sugar might be able to make it tractable. But maybe you're better off writing that code in a different language, anyway. C has a good thing going, so why risk messing with it?