Aang will be pretty open about where he came from at first, then gradually clam up more and more about it as he realizes that literally no one else has dealt with the same thing and everyone is giving him pity eyes when he randomly says stuff like 'I've lost count of how many times I've died.' He also might at some point 'casually' ask Anders how hard brain surgery is to do if, say, someone has a thing in their brain that they want to remove.

It's like Aang's job to save people named Bucky from themselves. Aang would be the little shit to jump in and slap a sticker on him in the middle of a super serious broadcast. And then Bucky can casually wonder if this is the ghost of Snow punishing him for his rebellion.

Then hold on to your pants Anders 'cause Justice will not stop. He'll go into all the dirty details, from Leilani's ears to how much she likes it that Justice can shapeshift into a woman when he's feeling it.