That appears to be a dead body.
I did notice someone clipping through the floor last night, though. As I was /reporting him, he popped out and shot me with his rifle, but only wounded me, and my MP40 did more than just wound him. :-D
That said, the game is buggy enough that it's not usually the person's fault when they do clip. I forget which town it was, but a few weeks ago, every time I spawned in, my feet were stuck underneath the ground.