Hmmm ... So I can see what you're saying about his change, but that felt like a natural progression to me that he would try to be more jokey. And he still had tat asperger's-like misunderstanding of what is socially appropriate, a la the "Hahahaha you just told everyone your deepest, darkest secret" scene. I'm a bit biased, since Guardians are some of my favorite Marvel films, but I just didn't see any character changes between 1 and 2 as jarring.
And I wouldn't know him from any of those places, so it must be the voice, but great for John! (and you; forgot you were in a movie). I'll have to check out that one and Zero Charisma, which I have seen the trailer for.