What hidden behaviors? The only hidden behaviors I can think of which are somewhat problematic in C are implicit value-changing conversions. But one can instruct compilers to diagnose those.

> Not hidden, the C standard spells it out

I would argue that if it needs to be spelled out in a separate document from the code you're reading, then it's hidden.

You must be joking. Like, you only use languages that don't require you to learn anything.