You would say "why not?". I would ask you would you let a Camalot Paladin into your all thieves game? Would you let a guy in a bozo the clown suit (and must wear it all the time) into your espionage team? Would you let a guy in a bathrobe and pointy hat who claims to be a wizard (and is) into your science fiction mercenary campaign (okay you might). Now if we were running a different kind of game, sure the character would work. If we are running a comic book styled game... no.
See, you are pushing my examples to the extreme trying to prove a point.
Yes, i understand why anyone would disallow such extreme examples. What i am asking (or have been asking) is for you to draw me the line (me as a player) where i break genre so i dont cross it.
Aka: when do i stop dodging. No, extreme examples with clowns, etc are not really helping me.
Supers games tend to be about "powers you have" and "powers the GM approved". Going beyond that because you logically should be able to, you have basically decided to ignore character creation and game rules. Minor things, okay.
So given my example of Flash powers and Punisher personality you as a GM rather ban the personality, i would rather ban the powers.
Major things, it would be like a fantasy character casting some spell (you would then say, you can't not on your sheet... he would say it is logical that I could). If you want to use reality to do certain things, that is okay. Your GM might let you. Then you will discover that reality cuts both ways as that piece of road debris rips through your thigh like a large cal bullet.
no, imho that example is wrong. That spell you describe would be like me asking for my power to do something it does not, like for example stretching for more than i can, going faster than i could or lifting more than i should.
My example of creative application of powers is more along the lines of "i use my fireball to ignite that oil" which most games can handle and allow but in a super games a similar application would be breaking the genre because i suddenly became too smart.
Genre compliance is a spirit of game compliance. One of the reasons many people have unsatisfying Supers Games experiences is because either the GM or the Players "don't get it". (Don't believe me, look at the number of people in the favorite/ least favorite thread). Sure they are playing the "playing smart, and if I had powers we would do it this way", but that won't be a comic game.
Here is where i disagree with your pendragon comparison. I am playing a knight that cares about honor, thats why i act in a certain way. My personality dictates my actions.
In your vision of a super example, i am playing a smart person that is stupid. There is no personality that dictates those actions. Imho, it is quite different.
Also regarding "people getting it" i think lots do, the difference is how they refer to it "putting kid's gloves", "dumbing the character down", etc.
Now i dont see many people saying this cant be played, it surely can. But since, as you said, it is quite difficult to put in game mechanics, the responsibility is on the players to keep the strong powers in check. For many people this is boring or just too hard for a given group.
However if there was a system that took away that responsibility to throttle from the players (and hence this thread), many more people would find it more fun.
To address one last thing...
For me at least, this would totally suck to play.
Hence why you should not be playing. And that is okay. You are not a supers player. The bit about Supers Play is trying to show how good you are by how well you can work in their rules. Just like a Noir game is about showing how well you can be the cynical protagonist, or a Pendragon game about being a honorable knight. Any of these may not be their cup of team. And that is why we have so many different kinds of games.
I could play a supers game perfectly fine, even if it was in your point of view, i would just find it boring to have all this cool powers and not be able to use as i see fit.