It's a neopronoun, some people prefer those over the widely accepted ones in their languages ^^ As an example, in some languages, there aren't neutral pronouns at all so neopronouns are necessary to achieve that. It's the case for many romance languages. In Portuguese some people proposed "elu" as a neutral alternative to "ela" and "ele", so it's a neutral neopronoun.
How common it is depends on your circles I'd say.
How common it is depends on your circles I'd say.