Does this ability traight stack if I have multiples?

SHARE THROUGH THE WORLDMIND:#Friendly characters with the Nova Corps keyword can use Ranged Combat Expert, but using it modifies their damage value only by +1. Give an adjacent friendly character with the Nova Corps keyword a power action and modifiy this character's damage value by +1 this turn.

Are you asking if you can give Multiple Nova Corps member each a power action to increase one character's damage value by more than 1 for the turn?

If that is the case then yes, absolutely. If you have three characters with the Nova Corps keyword standing next to the character with Share through the Worldmind and give them all a power action each, that character would get +3 damage for the rest of the turn

Ok cool thank you

the first part of the power grants a limited RCE, as as such only applies once. The second part is much like the power action part of the SHIELD team ability, and as such can be applied as many times as you have power actions to give to adjacent NC figures. The total modification, though, is limited by the Rule of 3.

Ok so would you only have to have two adjacent to get the +3
One from having the ability and two from adjacent?

Correct, the Centurion would use RCE from the trait for +1, then 2 adjacents each use the power action from his trait to do another +1 each.

Right. The value to going over 3 in the plus column is to offset possible negative modifiers.

So would this be more of a casual or tourny type team?

Can any one answer that or has nobody tried?

Well, it's not really a rules question, is it? Things like that belong over in the strategy sub-forum