My metafiction Batman headcanons:
The Joker can 100% see through the 4th wall. He knows he's in a comic book, which is why he thinks death is funny -- he knows it's fake
This is also why he freaked out so much re: killing Jason, bc he knows you don't kill the kid sidekick except now they have
Thanks to his death and resurrection, Jason can now touch the 4th wall. He could see through it if he wanted to, but he loves people (coughBrucecough) too much for that
Similar to Jason, Barbara touched the 4th wall upon becoming Oracle. She has less trouble sliding back into normal character awareness though, since she started as a TV character
Talia used to be at the average 0% ability to see the 4th wall. This has changed with her constant back-and-forth good/evil characterization, so she is now aware of it enough to slide into her role
(she knows playing her role well is the best thing she can do for the ones she loves, because her story will always serve theirs)
Damian's early memories of his mom are always shifting. Sometimes he can't even remember her before he was 8. It's easier to just remember she loves him, because that's the only thing that stays constant
Bruce has existed long enough he should be able to sense the 4th wall a little, but his brain physically prevents him from doing so bc he would spiral so badly
By sheer numbers Dick is also old enough to notice something, but he was a kid/teenager for so much of it that he just goes "wow my childhood was WILD"
Cass would be a little aware of the 4th wall if her childhood wasn't so messed up that she just thinks the weirdness is normal
If she figured it out she'd probably spiral like Bruce
Duke can feel it a little, but he never thinks about it (he's focused on the people in front of him) so he genuinely forgets
Steph figures it all out in college when she takes a philosophy class, but since it happens off-page she doesn't actually know they're comic book characters
