There was no advantage in Al "Atom Smasher" Pratt killing his Earth One counterpart since he was still following Zoom's orders, and left the corpse in plain sight to be found, so that the authorities would be alerted and close down his identity.
In season one SG1 when Carter crossed over through the mirror, the special effects used made her look like Barry Allen funking out to air guitar at super speed. Her companion Kawsolski(sp?) was fine becuse that worlds version of him died in the pilot.
10 years later, when there where 30 cross dimension editions of SG1 aboard an Earthican Starship, no bugger seemed to be tweaking even though there were 30 Sam Carters rubbing shoulders. Although since they were in N-Space, out side of the universe that might explain why the other dimennsional space the ship was in didn't give a shit about how many Carters there were.