Board Thread:Suggestions forum/@comment-26371213-20151227213442/@comment-25101089-20151228190550

Spears do not go through NPCs. They have exactly the same behaviour as arrows.

Friendly mounts do hit each other. They simply don't deal damage. In fact it is exactly this reason that the arrows bounce off: if the arrow hits an entity but doesn't deal damage for whatever reason then it is coded to bounce off.

These characteristics cannot be "implemented together", whatever that even means, and like I said above, it is impossible to edit the arrow code.