I wonder what hardware configuration that other person was running.

I’ve not seen anything like that in Safari on my MacBook. (Older than yours, if I recall correctly).

That video looks like a video card driver problem, something in the refresh during the scrolling operation. Have they changed the video subsystem since the introduction of the MacBook?

My config for the graphics:

Chipset Model: GMA 950

Type: Display

Bus: Built-In

VRAM (Total): 64 MB of shared system memory

Vendor: Intel (0x8086)

Device ID: 0x27a2

Revision ID: 0x0003