I'll admit that I get queasy when the term "soul" is mentioned in relation to a Joss Whedon soul. He's fond of throwing the term out with ever really saying what he means by that.

They wiped all his memories out thanks to their technology
I don't think they did. Everything we saw on the show points to the memories still being there, but behind a subconscious barrier (explaining the previous personalities surfacing in the episode when they were all high).
What