What you have there is "filiform corrosion". It won't buff out easily. I think it looks alien and organic, akin to mycelium, and is aesthetic to my tastes. I wonder if gun blue would stain it?

p.s. I have been contemplating a similar approach to my Ghibli, going plain Jane no makeup "warts and all" in defiance of Rossin's standard of over the top ostentation. After all, it's a Rossin and apparently anything goes?