Not allowed, one neutral per hole, you may double up on grounds provided instructions (panel labels) say so.
Is this panel GE? I see it frequently in older panels, Square D QO is the biggest offender followed by GE where those panels had limited neutral terminals to start with so doubling up was very common.
The reason behind not allowing doubling up (among isolating circuits) is that one conductor may be held in place more by the screw than the other conductor. This can cause further loosening and overheating down the road.