You're right that the Superman aspect of his memorial is indeed trivial. It's so trivial that DC (or any company in their right mind) would have simple approved it with a rubber stamp and maybe (at most) issued a simple statement about how tragic his death was.
It was only by denying such a simple and trivial request that DC's *FUCKING CLUELESS* legal/public relations people turned this into a story, not about a kid's tragic death, but about a company so callous and clueless that it would deny something so simple and decent that wouldn't have even cost them a dime--just out of reflex, it seems. What could have been a simple story about DC letting the Superman symbol be used for a small memorial for a child who died tragically has once again turned into a story about the clueless leadership at DC and raised more questions about the culture-of-clueless-fuckup that seems to so thoroughly pervade that company and every decision they make.
Of course, it also doesn't help that Superman is a classic symbol of human decency--a symbol that DC has sullied yet again with greed and callousness.