I've been having this discussion with a co-worker for a while now and figured I would throw out here:
Obviously, color maps, the pixels we want our screens to display, need to be converted to Linear and fed into (let's say) UE4 and we check the sRGB box on.
Information maps (as I call them): Spec, Roughness, anything that provides scalar info from 0 to 1. If we are painting them in PS or Mari or Mudbox, we are painting what we see through the monitor, which is providing us with sRGB gamma 2.2 images, are our gradients truly Linear? OR do these maps need reverse gamma correction applied before they go in engine (understanding that we leave the sRGB checkbox off)? Normal maps are an exception because they are baked, not painted (hopefully), but regardless, is 50% grey really 50% grey when I throw that map in a shader? In my mind it isn't, but I know there are a few people here that can clarify.