Maybe, but if you get more chances to shine, chances are you're going to shine more. I wasn't implying there was a direct correlation between them, but yeah as x approaches a certain amount of spotlight, y is probably going to seem less significant.
It's true, Rowling didn't develop Sirius' character nearly as much as she could have, but in my opinion she developed him enough. He's a compelling character, though of course not everyone will feel the same way.
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