In panel boards the bonding terminals are approved for 2 #14 or 2 #12 Cu and 2 #12 and 2 #10 aluminum wires. This information is on the piece of paper that came with the panel you throw away without reading. Neutrals are approved for only 1 conductor.
4-026 also requires that you should be able to disconnect only 1 grounded circuit conductor (neutral) without disconnecting the neutral from any other circuit. A terminal with 2 neutrals if loosened to remove 1 wire would possibly open the other.
