If parked flat I never hear it, but incline/decline parked for long period I hear the rattle too. I had the car at the dealership overnight for another fix, but I told them about the rattle and asked that they observe the next morning. Of course, not able to duplicate, so nothing done.
I'm skeptic to get anything done about it if they do find it. Last car I had had the rattle, under warrantee they went in and changed timing chain, guides, spring tensioners, did it over 2 jobs, apparently they missed something. Thing is, the rattle was still there even after all the work, including an oil leak that they could never solve. after about a year of chasing my tail with it I traded it in for the Cadenza. So long story short, I've been burned, I'm willing to just let it go, it's under warrantee so if the chain breaks, I'm covered to 100,000.