Well, I've got it...the dreaded aluminum pitting on my MBP's palmrest. There are various theories out there as to what causes this, most notably something about the pH level of certain people's sweat or electrolysis due to the machine not being grounded. Either of these could be the culprit as I've never tested the pH of my sweat, and the crappy type F plug adapter Apple sold me does not have grounding strips. Whatever the case, it has happened...and it looks bad.
Unless someone has a better idea (I don't really want to buy a replacement palmrest), I'd like to simply buy a non-transparent palmrest protector to cover it up. There are tons of them out there for the unibodies and other newer models, but as I've said before I'm rockin' a 1.83. I'm pretty sure the newer models have trackpads that are a different size from mine, so they wouldn't fit without some cutting and I'd rather not risk $25-$30 on messing up.
Does anybody know whether it is still possible to get palmrest covers that are cut to fit my model? I haven't been able to find anything.