Also, I still maintain that Damian in Supersons (both series) isn't the real Damian, like this Ian character in the Ink (or Zoom?) book.
Damian doesn't need to be acting like a child. He shouldn't even be acting like one. It's not who he is, it's not what makes him interesting. Playing up the discrepancies between his age and his outlook on life, personality and behavior is good (like when Maya made him lose his final baby teeth - I don't know the English term, we call it
dents de lait in French) because it's both unnerving and strangely impressive to see a child/teenager having both those moments of innocence (not childish innocence either, but always something very deep and emotional) contrasted with is usually ruthless behavior. But to me it's clear that Damian whole personality, outlook and behavior runs contrary to him not only wanting but acting like a child.
He can have some quirk, like playing games secretly but even that isn't limited to kids. But having him behave like a teen years old and enjoying it, when he wasn't turned into a senile old fool or otherwise ridiculed, was a disservice to the character. Not all kids needs to be acting like one, when their background and development run contrary to it.