I just encountered the following sentence in The Oxford Guide to Style (p. 161) and could not figure out its structure:
Since it⁽¹⁾ is being presented as a direct quotation it⁽²⁾ is treated as one, it⁽³⁾ being immaterial that the words are not in English.
Why can the the final instance of the pronoun it, the one labelled with a superscripted ‘(3)’, be inserted at the end?
The first two instances of it, those labelled (1) and (2), are clearly coreferential to the same earlier antecedent (whatever is being presented as a direct quotation), but what is the third instance of it referring to?
What is the grammatical structure of this sentence?
Can that third it be omitted and the sentence remain grammatical and unchanged in meaning?