One valuable property of C that the author didn't hit, C code is easily translatable into assembler in your head. He kind of misses this point with the virtual machine discussion. Yes C code becomes different types of assembly by platform, but you can look at C and have a clear idea of what the assembly will look like.

This is at a really good level for driving intuitions about what the computer is actually doing. Your concern 99% of the time when you are trying to think at this level is performance, and thinking in C will give you the right intuition about how many instructions your code is generating, what and when memory is being allocated, and which exact bytes are being pulled off the disk for certain function calls.

Modern swift/java/javascript compilers are so good that they will often generate better code than you write. This often makes knowing C a less useful skill. But, even so, when trying to understand what a compiler optimization is doing, you are probably thinking in terms of the C code it is generating. It's at exactly the right level to be clear about what is actually happening without drowning yourself in JUMP statements.