Mick Hartley

The Chicago Manual of Style is a guide for American English published since 1906 by the University of Chicago Press, dealing with aspects of editorial practice, including grammar and usage, as well as document preparation and formatting. In its own words, it's "the indispensable reference for writers, editors, proofreaders, indexers, copywriters, designers, and publishers, informing the editorial canon with sound, definitive advice". 

And, as the LA Review of Books informs us, the 18th edition has just been published:

The newest edition is billed as “the most extensive revision in a generation,” one that “balances tried-and-true editorial logic with an attention to real-world usage based on evidence that is easier than ever to find and evaluate.” This means (one shouldn’t give away the whole plot) that there are critically important new passages born of a deepening social responsibility in line with the times: how best to render text accessible to consumers with disabilities, a brand new section on inclusive language, guidance on Indigenous languages and sources (and rules advising that we capitalize Black, White, and Indigenous), and an endorsement of the singular “they” as a pronoun for an individual—“as needed,” the editors write, “to refer not only to someone who is nonbinary but also to anyone whose gender is unknown or irrelevant (or concealed for reasons of privacy).”

Not just describing the use of the language, then, but pushing it along on the correct ideological path. "In line with the times" indeed.