Hello! I worried about my Liquid Cooler because the Block have scratch. I was gonna replace new thermal paste until I saw there's a scratch. Should I worried about this? Because it has 7 months since I bought the item. The Cooler was Deepcool Gammaxx L240 Liquid Cooler.
Here's the picture.
I agree with CountMike it's really too small to make a difference... but if you're in that enthusiast class that borders on OCD you could polish the surface to remove it.
Take a sheet of 2000 grit emery paper and tape it to a sheet of glass. Then lay the copper heat plate flat on that paper and just rub it in a figure '8' pattern for a few minutes. It should polish away fairly quickly.
It probably happened by scraping across a piece of metal while being installed or removed; possibly the stand offs it mounts to. And really, that's way too much effort for the benefit it will provide. But there are those who find it necessary.