Thought I would chime in on the thread, although it's quite old and unanswered.
I am noticing something similar with my '24 ST.
Going to pop the tail light out and see how it looks.
From what I can tell, looks like the tail light either rubbed or was aggressively installed at the factory and scratched the paint. I found a similar thread on a Focus forum where they had to shave some of the tail light off to keep it from touching.
Good thing I asked for a touch up pen when I picked up the car!