I’d suggest if you are going to do this to your MacBooks to get the silver one. The silver one is actually aluminum and no one would notice.
They’re all actually aluminum, anodized to the color you choose. The silver one is the only one not anodized.
Filing off the anodized layer is indeed bound to look awful.
I’d actually be interested to see it on a black one. It might look like “brassing” on an old, well used camera.
Whilst I like that it increases the “tooliness” of the Mac it’s not of me I think.
I like mine pristine. ”There are many like it but this one is mine”, yada, yada.