To answer the questions: I've never heard of "Stacy" and incel slang would get no sympathy from me.
"john" feels more like an established synonym, but if someone named John complained I would try to use other terms, it's not hard. I don't think I use it much anyway.
I have non-white friends named Karen who have said they find the new slang hurtful. They don't like seeing their name turned into a term of opprobrium, oddly enough. So I'm not just making up a problem.
Okay, I'm done with the tangent