Sogeking is not a split personality, he is a fictional character made up by Usopp, that conversation was between Usopp and him self, he wanted to know what Sogeking would do in his situation so he conjured up a Sogekin personality to help him self, this is purely mental and not a real condition. It's like when someone does something and argues with them selves in order to find flaws and discovere possible improvements. In Usopp's case he has set a role model for him self in his own mind and is able to act in character of that role model. Not a split personality.
I don't know, Usopp didn't think, "WWSKD", he cried out for Sogeking to help him. Then he had a mental conversation with Sogeking. Usually when somebody is making a decision they don't converse with themselves in this way. It would be more like, "Okay Usopp, calm down, Sogeking wouldn't act like this. Sogeking would analyze the enemy and find her weakness." etc.
Originally Posted by 12LetterName
Maybe you're right, but I think it's definitely debatable.