Right mate, speaking from experience, and recent too:
You WILL scrape it - I've parked in a carpark space where length is a bit of an "issue" (for some reason spaces are short and people have to squeeze passed the parked cars) and I've hit the kerb at the front of the space a couple of times. It makes the front of the car a good 25mm lower at the tip.
Also multi-storey car parks, if not negociated properly and SLOWLY, you can scrape them. Now, it doesnt notice as its on the UNDERSIDE of the splitter - but if it was painted chances are a chip would occur and it'd look pants.
I totally agree with the above - DON'T Paint it. It looks fine on an artic/platinum LCR, so will look just as good against the colour on an LC.
My car is now lowered and I've not damaged the splitter since the first 2 weeks of having it on the car - just takes some getting used to and control when coming up to speed humps etc.
Its easy to remove - you'll just have 8 or so holes in the underside of the bumper rather than lots of scrape marks. Simply remove the screws and it'll fall off. Dead easy to swap if you damage it too. (perhaps easier than the clips on the LCR!)
Seriously though, don't paint it!