Maybe "amazed and breathless" is a bit hyperbolic, but I assume the parent is referring to the number of people who had up-voted it at the time of his posting.
Perhaps for people who don't really know C, that's interesting information, but anyone who calls themselves a "C programmer" should not be surprised by that bit of code (well, you should be surprised if anyone still writes code like that, but not surprised that it's valid).
It's not even just an "exposed to legacy code" thing: C is a fairly simple language in both syntax and concepts (esp. when compared to most other languages people are using today), and I don't believe you can call yourself fluent in C without this kind of knowledge.
(I could also argue from the other angle: if you haven't been exposed to that sort of legacy C code, you probably haven't done it enough to call yourself fluent.)
I think it's an interesting question from the perspective of "what are some cool language gotchas that people not familiar with the language would find neat?"... or from the perspective of someone who is new to C, came across some code like that, and is trying to learn what's going on (and is apparently too lazy to google the C specification and spend 2 minutes reading it).