The first one doesn't seem like a good sentence to me. Probably I would understand it as a mispunctuated attempt at the second sentence.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Hans51I know a man I think who is honest.I know a man ,I think, who is honest.I know a man who, I think, is honest. This makes more sense to me than the others.