He didn't do it often—it would probably destroy him or drive him insane or worst of all break him in some unnamable way he hadn't broken quite yet. But sometimes… Sometimes, Zuko lay awake in that darkest hour, just before dawn, and he wondered who his scar marked more clearly: himself… or everyone else.
No matter how bad he usually was at reading people, no matter how hard someone tried to hide or suppress their reaction, that first second they saw the left side of his face also gave him a glimpse right down into their soul.
Not even his sister had been immune to it, that pre-dawn in the infirmary where she'd unwrapped his face with such unusually-gentle fingers and pulled the gauze away. And Zuko had seen it in her eyes for that single instant. For the first time in her life, Azula had known the fear of failure. Fear of their father.
Zuko had seen hundreds of first-looks and hundreds of souls bared for hundreds of single seconds since that first first for them both.
Looks of pity and looks of horror and looks of painful vindication.
The looks of disgust were particularly bad.
The looks of desire were so much worse.
Uncle's single second had been sorrow. Sorrow and such deep, painful grief that it had rivaled the loss of Lu Ten. Zuko would never forget that second.
The Avatar's single second had been blank incomprehension, because he was twelve and could not even imagine a world where scars like Zuko's existed, with all their implications.
The Water Tribe boy's, grim assessment, a potential weakness picked out and marked.
The waterbender's, confused disbelief, a mind scrambling to understand. Understand how a firebender could burn, understand the cause of the scar, the extent of the wound. Untrained, but still, ultimately, a healer's assessment.
(In the depths of his memory and deep down in the shadows of his soul, where he hid all the most painful, broken bits of himself where no one could see, he remembered Father standing at the door of the sick room, outlined in the light from the sconces in the hall as Uncle stopped him from entering. Catching sight of him over Uncle's shoulder, limned in firelight. He'd been smirking.)