Well, I looked it up and CGEL says the following: "It is used as a dummy subject with verbs and predicative adjectives denoting weather conditions, as in [It is raining. It became very humid.]. It does not represent a semantic argument and cannot be replaced by any other NP: it has the purely syntactic function of filling the obligatory subject position."
However, the authors address this (the comic's) very issue in the footnote: "There are some rather marginal constructions in casual style where it behaves more like a semantically contentful pronoun. It is trying to rain involves a kind of personification with it assigned an agent role by virtue of being subject of try; in %It rained and flooded the basement, the it is subject of a VP-coordination that includes a non-weather verb."
I think the sentence marked with % (which denotes that the sentence is grammatical in some dialects, but not all) is close to the one the linguist from the comic is wondering about.
I don't know what you mean by "in the old-fashioned sense of the word" – do you mean like "knowledge"? Haha. Because that's the original meaning (Latin scientia, -ae).
@s.patroller But I think sciences (in the more usual sense) like linguistics are more about categorization. Otherwise you could say basic human motor coordination is applied kinematics and dynamics (physics).
Sciences are categorizations of their respective subjects of study as well as relations between them.
(Just made that up.)
@s.patroller I don't think it's systematically organized at all.