I’ll write about this in more depth later, but this needs to be said now: If you’re writing Critical Role fic about Molly being nonbinary, you still really need to use his proper pronouns. He explicitly gave them to us. You don’t ever for any reason get to misuse someone’s pronouns.
There are nonbinary people who use binary pronouns. They have a lot of good and important reasons for doing so. They are still every bit as validly nonbinary for doing so. You are actively hurting people in your community when you don’t respect that.
When you refer to them with gender-neutral pronouns, you are aren’t exactly misgendering them, but you are complicating their identity and erasing what they have figured out. You may be causing them dysphoria. So just respect what people tell you is right for them.
I’m currently interviewing nonbinary people who use binary pronouns in order to write a longer piece. If you would like to be interviewed, please contact me. Your privacy will be protected.