I agree there is still a strong likelihood they are two sides of the same person. Whether they are a fractured psyche or whether this is a being who is consciously exploring these concepts and issues by intentionally acting as two people... either way, I strongly suspect they are the same being, ultimately.
Frankly, they look so much alike. Is it really a coincidence that Jacob and MIB (beach version) are the same height, same build, virtually identical hair style and length, same exact two-day stubble, same length sideburns, almost identical way of dressing (except for color contrast)?
Jacob fishes a red fish out of the ocean (just as he fishes people out of the world, catches them to use them on the island), sits down and eats lunch. MIB walks up. Jacob asks if he wants some. "No thanks," MIB says. "I just ate." Sure you did. We just watched you.
Carbonell is the MAN. Loved his performance! Exciting, sympathetic, romantic, passionate, tragic but also sometimes humorous and ironic... Such a complex performance, and he fulfilled everything in the character and then some. We finally, really understand Richard. I can't wait to see what happens with him next. Carbonell is now one of my three favorite performances on the show. Emerson is first, and Holloway second. (Ironic that my #1 and #2 play characters who I actually detest as human beings. But the performances are so layered, complex, nuanced, so familiar and real and yet also continually surprising in their twists and turns.)