So as an update, while the sample size is admittedly small, these interview "tells" seemed to actually work for me. I was accepted at both of these schools and was rejected from the school I thought was my worst interview (though, to be fair, that school has probably the lowest post II acceptance rate in the country).
Anyway, for what it's worth, it seems here that unusually positive things said by the interviewer were in the very small sample of little old me highly correlated with a positive admissions decision.
Good luck to all!