Nice,
1st I have read about a 08 smart reaching 10k.
I have heard a rattle before especially over a good highway bump, but then I keep forgeting to investigate for the location.
Just made me think of something I need to check out.
The fold down door/hatch, a few weeks ago, I leaned forward on mine, and noticed some play, when I pushed in and out, I heard a slight metal contact/click at the latch. I believe the seal is what keeps it out and tight. I have not looked into in detail yet and not sure if there is any ajustment in the latch area. Maybe its the rattle I have heard before.
Happy safe driving to the next 10k!!