I knew it. I read on the Wiki that in season five Murdock is declared sane. When he tells the others, in the 3rd ep, he's incredibly twitchy about it. I was thinking, either he just paid someone off or he escaped.
Episode 6, Hannibal tries to get him to come with him to a mental hospital so they can get a lead on their missing General. Murdock says nuh-uh, no way.
"Wait a minute, wait a minute! This little do-hicky says I'm perfectly and sensationally sane!"
This is what he hands Hannibal:

RAINBOWS!
Also, in... a very early episode:

Any theories on his writing skills? I need to study my psychology more, I think. LOL. Side effect/symptom of one psychosis or another? I googled it. All I'm getting is autism, everyone's recent favorite diagnosis (in general) for everything... I don't wanna be THAT person, although I can see elements...
Thoughts?