The substance? You don't know the meaning of "substance," then, is the disconnect? You go to the same page in italian just so you can seem more credible, or what? Even if not describing the flour then, even if that part was wrong - your little quotation from the italian page says "refers to a generic type of short tubular pasta." You know what penne is? A type of short tubular pasta, you buffoon. The point of the argument is that the picture shows macaroni and 'cheese', and calling it out that it's incorrect because "it's penne, not macaroni!!" is incorrect. Especially seeing as you then post a picture of something else that is clearly not the elbow macaroni that is thought of for macaroni and cheese declaring "see, this is macaroni!" Er, sorry, "maccheroni (because everyone needs to know that I'm super ***ing italian, and that's the only reason, not that I'm a pretentious sh*t)."

Link was included for a reason, but since you apparently couldn't be bothered:
"the term refers not to the shape of the pasta, but to the kind of dough from which the noodle is made."
That is, "macaroni is the substance, penne is the form." Sound familiar?

Macaroni is the substance, penne is the form. Traditional mac and cheese is made with "elbow macaroni," which is another form. It's all macaroni.
http://en.wikipedia.org/wiki/Macaroni