Ah, sorry…the final picture didn’t show it, but I did clamp the result from 0 to 1. Basically, backfaces (which were getting dot product results from -1 to 0) were being turned into numbers from 0 to 0.5 with that re-scaling of the range, and depending on the light properties/LUT/intensity/blah blah blah, could show some level of light.
By clamping those numbers directly (and not doing the + 1, / 2 thing), all results from -1 to 0 were being turned into 0, which is zero light, which is what I wanted.
I can still try to export the project but things are working exactly like I want right now! The barrel and material used in that test shot are entirely unmodified from the Sample map pack, I just added a red point light. (It was in a separate project that didn’t use my custom modifications, which mostly have to do with how it gathers lights.)