My name is Matt Chaboud. My username is my last name, and I'm easy to find. I try to behave online in a way that doesn't rely on anonymity (though I recognize that that carries some risk).
But I think your point is understood. However, a handle, to me, by virtue of convention, leaves little room for confusion as to whether it is a real or artificial/partial identity (generally).
I don't think I did a good enough job in my initial reply emphasizing that from my perspective a nickname that you only used in certian social contexts is functionally a persona. If your wife calls you Jason but all your drinking buddies call you Jack because of a hilarious collage hijink (or something), a random passer by at the bar would have no clue that the name on your birth certificate (the one that can be used to impersonate you) is actually Jason.
Thats really what I am talking about. As long as you dont lie about the fact that "Jack" is a nickname when asked, your not being unethical, in my view.