[drewrv]

Is it really that difficult to address people how they wish to be addressed?

If someone said to you, "Please call me Matt" do you respond with "But your birth certificate says Matthew! How am I supposed to handle this cognitive load? What's the benefit for me, Matthew?"

[ozy123]

"Matt is coming with us. He said he'd be at four. Jemima is also coming they said they'd be here at five."

Matt is coming at five? No Jemima is coming at five. Matt is coming at four. Also Sarah is coming with her partner Zoe. Ze said ze would be here at 4 also zey're getting a ride with Matt.

Umm. Ok.

Not to mention that now when I talk about women, I have to also consider every other gender non binary person as requested by OP. He doesn't want it to be essentialized and pragmatically to be inclusive one has to therefore moderate all language relating to gender.

That is a significant cognitive load and I wish people would stop pretending it's simple. I live around and have friends who are trans/binary non gender people and it's hard work keeping up.

[euyyn]

If you don't quite remember, or are unsure about, their preferred pronoun, it doesn't matter. Really, don't sweat it.

What we're trying to tell you here isn't "you should concentrate harder, learn it by rote, and never ever say it wrong". Rather: "just give it as much thought as you'd give someone telling you to call them Dave." No more, because nobody wants to make your life any harder, and any sane person would understand it if you forget. This is a preference, not an imposition.

And also no less, because at the end of the day it's a very little thing for you, and might mean a lot to them.

Grammar and plurals become weird? - You've already given it more thought than I think I'd have :) In my case, because I'm not a native speaker, I would have probably messed the grammar anyway.