So I ain't a writer by any training, but I was under the impression that quotations of the spoken word followed a separate grammar. That grammar is designed to capture details of how the person said something. For example, "Yes, I feel similarly" (and here I follow @goobster's rule) conveys that the speaker said it in a way that separated "Yes" and "I feel similarly". Two ways that could have happened are with a pause or by raising the pitch of "I". Meanwhile "Yes I feel similarly" conveys that speaker spoke in a monotone, or in a breathless rush of words.