Ki Seon Gyeom's mental state

 mpruel:

But actually we never know the truth lol

Yeah you can be right or not :D

This is the real beauty of the show to me. Whether or not he is on the spectrum not what mattered, Seon Gyeom is just Seon Gyeom. He's not shown off as, "hey we're doing something new and different." He's just another character, like the others... but different in his own way. The reason for that being unimportant. Either you see a connection to how he acts in yourself (in my case lol) or others you may know or you don't. He's still a really real person you could meet. I think that message is the most potent. 

On a somewhat side note, I disagree with getting angry easily... he holds it in better that 95%(totally made up statistic but you get the point) of people I've met lol. Anytime he does act out of anger it's planned for a result.
Although, I think you could add a stronger sense of right and wrong to that list, as he couldn't stand injustices.