I've got a neighbor I've already "freed" a civilian for. He's still unhappy with me, I've got another (or will in a turn here). If they're cumulative, I'll go ahead and let him have his settler back too. If I won't get any more of a diplo bump with him, though, I could really use the little bugger. Will I get another bonus for returning a second civilian? Also - I read the Diplo analysis thread, it wasn't clear to me from the posts there exactly how it works.