mr pi said:
The question is would supplying a 6 pin socket through an 8 pin power outlet damage the graphics card?
No. If you look at the 6 and 8 pin PCIe connectors, they both have 3 hot wires (the yellow 12 volt leads). The 2 wires of the "6+2" connectors are both extra ground leads. So either way, you only have 3 wires carrying power into the video card.
Speaking as someone who has been in electronics for more than 40 years (starting as a hobbyist), I just do not see how adding two ground wires is going to double the current carrying capacity of three hot wires.