The movie being officially released in a couple weeks has opened discourse about Zuko's scar being removed to casual fans across the Internet. People are coming up with all sorts of Watsonian reasons the scar is gone, but really it's completely illogical in any Watsonian way, sans some crazy situation where Katara found some special magical healing scar spirit water. In which case: 1.) why wouldn't she have healed Aang then, if he's her canon spouse? and 2.) I think Zuko would prefer his face scar healed.
That scar absolutely wouldn't be gone naturally, is the point.
People constantly seem to forget this tidbit about the lightning strike Zuko endured:
Azula is the most powerful and skilled firebender alive. She bends blue fire on an everyday basis, and we've never seen anyone else do this, even in Legend of Korra. She's crazy good. AND, this was on Sozin's Comet, supercharging her capabilities to the maximum level.
Also, remember, this is the power that Sozin used to take out the airbenders. It's like crazy strong.
Also yes, Zuko redirected the lightning, but clearly not all of it.
The video shows some of the lightning being redirected out of Zuko, but very clearly not all of it, hence why he's twitching in pain with lightning visibly being shown coursing through him for several seconds after the shot.
Now, Aang was knocked directly unconscious, this is true. Aang took the lightning fully, and he did die. His attack was more direct and severe, I'm not denying that. However, I think the show makes it pretty clear Zuko was on death's door. He can't even get up, no matter how hard he tries, and looks like he is fading in and out of consciousness.
But, if Aang was healed with spirit water (much stronger and more powerful than regular water, which Zuko got), in the same amount of time after being wounded, give or take, as we can see in CoD, then this still all makes no sense. Yes, Aang got struck more completely and directly, but he was also healed with the most magical, potent, sacred healing water that exists. If that's the case, and his scar still remains, why on earth wouldn't Zuko's, who got struck by Sozin Comet lightning and was healed with regular water…?
The fandom for years has pretty much concluded that had Katara not been there, had Zuko taken the lightning for whoever else-not-a-waterbender-healer, he'd be dead. I think that's pretty clearly what's going on here based on the powerful lightning that's struck through him — directly at his chest so close to his heart, mind you. That's an area that sustained direct, prolonged damage for presumably at least ten minutes. Zuko most certainly would have died save for Katara's healing.
Had he not redirected anything, he'd definitely be dead instantly because Aang was dead from a much weaker (though still quite strong) bolt of lightning.
Also, it's unclear how many hours to days passed between the gaang ending the war and the coronation, but the wound was still severe enough that Zuko was wincing in pain and struggling to put his shirt on.
On top of all this, this is an error the Avatar team (including Bryke's writing and direction) made before. In The Promise, only one year after this incident, his scar is completely and entirely gone.
However, in reprinted editions of the comic, this is corrected — because it is an error. It makes no sense. As Avatar Wiki even emphasizes, it was a "Comet-Enhanced Agni Kai", showing just how powerful that lightning strike was. And the fact that in the reprint the error was seen as worthy enough to reedit the image and add that in tells you that it was, in fact, a mistake and not something deemed actually canon that Zuko "got better" from.
So the artists noticed this themselves, or from fans pointing it out, and added it back in, and it was printed and published this way going forward. Zuko's scar is supposed to be there.
Which leaves us with three possible conclusions for adult Zuko in The Legend of Aang movie:
Bryke literally removed it on purpose because they don't want any trace of Zutara, friendship or otherwise, canon or otherwise, logical continuity or otherwise, showing up in their series.
They thought since it's on the front of Zuko's chest it takes away from how much of a thirst trap they were trying to make him (it absolutely would not, it would only ADD TO IT).
Bryke literally forgot because the continuity in their story matching up with the Legend of Korra timeline already makes absolutely no sense and they suck at remembering things about their own show.
Either way, it's disappointing and frustrating because they remembered Aang's back scar and detailed that in within the film, but didn't for Zuko. Which does make me inclined to believe option number one tbh. However, there's some benefit of the doubt considering that Aang's scar was animated for an entire season of the actual show, and Zuko's was the very last episode, so it wasn't something recurring within the animation notes.
