One of the top users for Politics.SE has a username like
[username]--Is RBG Dead Yet
Presumably in reference to Supreme Court Justice Ruth Bader Ginsburg.
I don't feel feel a username like "is (person) dead yet" (replace person with anyone famous) is appropriate, although I'm not sure it's in direct violation of the code of conduct or acceptable use policy.
Edit: I don't mean just famous people. I mean it's not appropriate for anyone, but, by way of example, replace person with any other well-known person and ask yourself if that's ok.