Hmm. When I was a child, I watched Superman2(I don't remember it is 2 or 3). I have been thinking that he works as both, and hides his identity as a superhero. Back to the ponint, do you mean that it depends on perception?I would keep "a". If he was known as both (if most people knew Kent was Superman), I might drop the "a".
Thanks for the correction. I really appreciate it. Can I have one more question so that I can be sure about it? I understand that in my example, it is better to put the a. How about this?That isn't a suitable example. A black and white cat is a cat that has both black and white fur. You necessarily have to drop the a there because both adjectives refer to the same entity; similalrly, "a black and a white cat" necessarily refers to two cats, one black and one white.
"Journalist" and "superhero" aren't adjectives in your sentence; they're nouns. The structure is different. You can't compare it to "black and white cat".