Merriam-Webster and they

Merriam-Webster explains the inclusion of nonbinary they in its dictionaries:

All new words and meanings that we enter in our dictionaries meet three criteria: meaningful use, sustained use, and widespread use. Nonbinary they has a clear meaning; it’s found in published text, in transcripts, and in general discourse; and its use has been steadily growing over the past decades. English speakers are encountering nonbinary they in social media profiles and in the pronoun stickers applied to conference badges. There’s no doubt that it is an established member of the English language, which means that it belongs in Merriam-Webster’s dictionaries.

The “grammatically conservative” might want to read this short commentary by Geoff Nunberg. The sentence that hit home for me: “It's not a lot to ask — just a small courtesy and sign of respect.”