Remember, as long as all the electrons
stay on the ball, the entire ball's net charge
is neutral, as long as everything added up together
still equals zero.
If the balls do touch, the electrons have the
chance to move from one of the balls to the other.
This would produce two positive balls
but they would have an even distribution of electrons.
|[- + + -+ + -++]
||[- ++ -+ + -+ +]