I do not have any input regarding the scratch resistance (or lack thereof) on the HE508T. Best advice, as I'm sure you know, is to only use an optic-quality, clean microfiber cloth to clean the window.
My long-term experience with the SIG ROMEO1 shows that even a careful cleaning regimen can't avoid minor scratches on the lens, mostly due to objects hitting the window. I don't seem to notice them, especially at close range.