Elliot S! Maggin speaks about Superman and Clark and Lexcorp in answer to a question from Quora on this
Forbes page.
I more or less agree with Maggin, but his answer is a bit too simplistic--a necessity of these kinds of sites, where one can't really talk at length about what makes a character. NOT as simplistic as those that try to reduce Superman to an epigram--Superman is the mask/Clark Kent is the man OR Superman is the reality/Clark Kent is the illusion. These sayings sound good, but brilliant people have spent over seventy years and millions of pages writing about the character--do we really need to reduce such a complex construct to a nine word statement?
One of the stories that made me really think about Clark Kent was that Maggin Private Life of Clark Kent story, where Elliot quotes Kurt Vonnegut (from Mother NIght, I believe) to say something like we must be careful about the masks we choose to wear, because one day we may find that's who we are. I'm too lazy to look up the exact quote, although it's easy to find. I'm sure I got it wrong.
In that Clark Kent story, I felt that Elliot was saying Superman had gone about creating the character of Clark Kent, thinking that it would be just a mask, but ultimately this mask became his real identity.
In one of the novels, Maggin suggests that Clark Kent is like some perverse hobby of the Man of Steel. That Superman devotes a lot of energy to create this character that is just an illusion. This didn't sit right with me, because it made less of Clark.
The basic schism between Superman fans arises because Byrne erases a lot of the back story that had accumulated over nearly 50 years of Superman stories. At one time, Superman remembered his childhood on Krypton. That was his primary ego. His experiences as Clark Kent were written on top of his experiences as Kal-El. Once Byrne took Krypton out of the equation--because Kal-El was only a fetus on Krypton--it seemed like the formative years of Clark Kent were Superman's primary identity.
This is splitting hairs. I wouldn't say that Kal-El/Superman/Clark Kent has a multiple personality. To say that is to interpret the character as suffering from a mental illness. Superman has different personae, but he's a fully integrated person (albeit a fictional one). Like all of us, Superman slides between different roles in his daily life. We don't ask ourselves--not most of us and not most of the time--Who is the real person? when we slip from one context into another, where we express different sides of ourselves.
Frankly the question shouldn't even be asked. What are people after when they ask this kind of question about Superman? Why do they need to pin it down?
If you read the early Superman stories by Jerry Siegel there isn't a clear division of personality traits. At least when I read those stories I don't see that. Rather it's this kind of existential idea of personality. Superman (or whatever you care to name this guy) is the person that he is at the time that he is doing something. So sometimes he is a nerdy or cowardly Clark Kent, sometimes he's a heroic Clark Kent, sometimes he's a heroic Superman, and sometimes he's none of those because he's some stranger in civvies who has jumped into action. He's really this protean type of character that Siegel wrote--one that took on whatever traits were needed for any given story. But this existentialist definition of character may be more real than later attempts to drive a wedge between Clark and Superman. We like to pretend we have a consistent character and others will try to put that on us. But really, we're all just winging it. And we have no idea how we will act in a new circumstance. Which is why people so often surprise us when they seemingly act out of character--either by saving people from a fiery plane crash or participating in a destructive riot.
But the main point that Maggin is making is an important one. The comic is called Superman. This is the larger than life character that we signed on for. Clark is an interesting aspect of that, but the heroics, the powers, the red briefs and capes--that's the true character. It's because he is so noble and so inspiring that we read about him. It's also interesting that in some Christly way he humbles himself through the personality of Clark Kent. There's no need to question that. It all works.