Yeah, I'd have to agree with you on both of these. Possibly it's my bias, but I think the Rodney fanon is worst because, as you say, it doesn't just affect how people perceive Rodney, but everyone around him. It's pervasive that way. John Sheppard fanon can be really annoying too, but doesn't tend to affect other characters to quite the same extent (at least as far as I've seen). John acting like an emotionless robot doesn't turn Teyla OOC, for instance.