Stephen Day wrote:
I'm sure there isn't one, but in the end, that doesn't matter to what I'm saying. He can call either one Kate or Kathy. As long as the people he's talking to understand who he's talking about, what does it matter which one he uses?
I think it's akin to referring to Aquaman as "Artie" or something. Sure, it's another name for Arthur... but you just wouldn't do it. Because it's not his name. And you wouldn't call the Human Torch "Jonathan Storm" either. Sure, it's a form of his name... but his name for all intents and purposes is Johnny.
These characters have shortened names for distinct reasons. And when you've got two characters with basically the same name, that distinction is even more important.