Furthermore, I really don't think a comment should be used to explain a language element that is clearly defined in The C Programming Language (K&R) by Brian Kernighan and Dennis Ritchie. A C programmer should assume the reader is familiar with what is in K&R, otherwise the comments become a language tutorial.
I generally agree that comments shouldn't be required to explain language mechanics unless they are obscure (which the bitset stuff isn't, I mean if you've never run into them they might be, but that would be the same for any language construct and as you said, you generally assume a developer is going to know the language they are working with).
What I personally would generally include would be a comment along the lines of "this struct represents the KillAllHumans message body as per <some specification;>" where the struct is defined, and then a comment along the lines of "overlay our message structure over the buffer to extract our data". This way even if someone wasn't familiar with the bitset notation, they could probably infer it.
As for Perl, once I really learned Perl I found it to be extremely intuitive. It is a very powerful and very expressive language. All of the sigils (and related "line noise" characters) make the code much easier to read and they make it extremely trivial to define and understand complicated data structures. Larry Wall, the creator of Perl, got an undergraduate degree in natural and artificial languages and then went on to do graduate work in linguistics.
Perl... easy to read... ok back to your room now ;p
I'll grant you that perl is very organic, probably the best "code as you think" language that I know of, but the vast collection of syntax and the functional density one can achieve (and some seem compelled to do so) makes it a pain to read if you didn't write it.
I've read the camel book cover to cover, and at one point I was fairly good with it, but after a few years of neglect that skillset has completely dissolved. I have a feeling if I tried to do anything with it now, I'd be hitting up google for things like "how do you iterate through an array of hashmap references".