While negative reflectance is pretty cool I highly doubt this will become a feature and negative reflectance will probably be gone in the future. You’re pretty much using a bug to get this behavior and it’s kind of amazing this isn’t simply clamped already.
I just figured if the “bug” exists for normal parts, I could do a lot with players parts as well. If they remove it in the future then I’m content with that. Thank you for the insight!