I don't personally run requests like this through an internal filter to figure out whether or not I agree with them or whether they make sense to me. To your point of titles:

> But a personalized pronoun is like someone informing you that they identify as a doctor, even though they have no degree, and you must therefore address them as Dr.

I don't think I've ever looked up someone's PHD after they asked me to call them doctor. I just do it, it's no skin off of my back. If I find out that they're not a doctor later, I might think that's kind of weird, but I'm probably not going to fight them over it.

Same if someone says they got married, or if they're getting married and keeping their last name, or if someone gives me a pronunciation of their name that doesn't match phonetically with how it's spelled. I don't really know that I have a validation criteria for any of those things, I don't think I've ever needed one.

I guess I can theoretically think of examples where it would be an issue, but I've never personally encountered them, and I don't think xe/xim rises to that level. Memorizing xe/xim isn't any harder to me than memorizing how a name is pronounced.