Admitedlly, I haven't read all 6 pages of this thread - there are some kewl ideas here, though., so I apologize if someone else has thought of this as well.
I'll throw my two cents in - I'm pretty sure that it will ahve something to do with everything that Brandon showed us about the Ideals that were spoken in Oathbreaker - primarily:
Dalinar forgiving himself and Teft learning to live with himself, seems to be the central theme here (forgiveness) - and Kalidin has extraordinary problems doing that, sure, but there was more to it than that, I believe -esp. when he knew that he could/would receive a 'burst of power' by saying it. It didn't seem like enough of a painful barrier.
I think it may be somewhere along the lines of :
"I will let my failures and the ones that I have failed give me strength."
Seems to be something that Dalinar managed when he took his own pain from Odium, and Kaldin just cannot do that yet.