Are we allowed to use the same lightning bolt effect more than once on a single attack e.g:

Roll attack result: lighting/lightning/damage/damage, and my weapon has a lightning: +2 damage effect.

Can I use the +2 damage effect twice to make this a 6 damage attack?

No you cannot use the same surge effect twice per attack.

Thanks.

You could use it if you have the same effect printed twice on the weapon (there is one such weapon in tier 3 i think, can't remember what its called) or on the weapon and attachements.

~: +1 Dam

~: +1 Dam

~: +2 Accuracy

just like the golden rule, each effect may be triggered once when it may be triggered. if there are two identical "effects" like in my surge example, both may trigger once.

Not unless you are a saboteur.

I think what he is saying is in the below example:

~: +1 Dam

~: +1 Dam

~: +2 Accuracy

You could spend two surges to get +1 damage each, because it is printed on the card twice (one surge for each printed ability).

Whereas in the above example, a Saboteur could spend up to two surges per printed ability and get up to +4 damage with 4 surges.