in v7 put a noise bump on a random object, use value 100 and render, for caparison do the same with negative 100, the indentation now became elevations and vice versa. in v8 that is broken for a real long time it seems, rendering with 100 or negative 100 makes zero difference now.
i never hat the actual spirit and time to have a closer look before and render the same instance out twice to see if i am dreaming but i am guessing that this might have happened maybe even more than a year ago, i did not log my first suspicions though but i am certain it is in there for a while.