Quotation marks are often used for purposes other than reporting speech. A common use nowadays is the 'scare quotes' or 'air quotes' where they stand in as typographic or even mimetic symbol of irony. A synonym for 'so-called', that distances the speaker or author from the particular word or phrase they are using.
But yet another use is to highlight the introduction of a new concept with which the author suspects the reader might not be familiar.
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