Yeah, there's kind of a perceptual/patternmatching arms race going on there -- if you're too blatant about it, or the intended recipient of the reinforcement is just that perceptive, then they're reading the script too and it won't have the intended result. It could backfire (as in your example; semantically-positive reinforcement becomes pragmatically-negative), or send undesirable information ("you wouldn't have put it that way unless something were up, and that gives me a clue"), or open you to counter social-engineering scripts if the part knows what they're doing.