Hart- Er, I think in Jung's terminology. Here's what an
ISTJ description. None of the descriptions can be exactly right, but they're a general personality trait theory. I've studied Jung's meaning of the personality traits, so I have a fairly good grasp on what they are exactly, though the descriptions typically rely on mixing the traits. I don't mean to be too detailed about it though, so if I'm not making sense, just ignore this- the thing I'm trying to say is the link there.
I'm not sure what you mean by off-handedly... I guess I have a hard time applying it to Shin. Mikkou is fully aware of his flaws, he practically flaunts the fact he's a lazy, perverted, irresponsible, angsty person. And he's a thinker so he'll muse on them, but he ends up not caring. Morris constantly focuses on his flaws, which are almost all internal. Nuke doesn't think he's flawed, he thinks everyone else is the problem.
Anna (another character) is a lot like Shin, but she's more likely too preoccupied to notice her own flaws.