Originally Posted by ThePhantasm
In TDKR we get no indication that his symbol endured, in fact quite the opposite - it is established early in the film that Gotham thinks Batman is a murderer, his reputation is tarnished, etc. The symbol only endures in the mind of Gordon and a few older cops (and the orphans). Everyone else is hungry to take Batman down. The symbol didn't endure because Batman just hung up the cowl and gave up on the symbol, rather than continuing the fight.
In all fairness, his symbol certainly endured and saw retribution by the end of TDKR. You're talking about the first 3rd of the film as if the story ends right there.
TDKR is a complete continuation of TDK, and BB before it. Despite a "fall from grace" (typical superhero trope) after the events of TDK, Bruce's mission as Batman should still be considered a triumph, especially after what he did for the city at the end of TDKR.
At the end of TDK, it's stated that Batman is "the hero Gotham deserves, but not the one it needs right now." But by TDKR's end, it's clear that Batman filled both of those roles. He came back. He was needed, and he did all that he could to protect his city. He DID endure, and despite Bruce seemingly moving on from it all, the ending of TDKR suggests that the Batman symbol will endure, too.