Rear axle adjuster on left side??

The reason the adjuster is put on the right side instead of the left is because the adjuster would not loosen up if somehow the lock tang was to break or be accidentally left off. The adjuster would tend to want to turn in the direction of axle rotation. If it was on the left side, that would be counter clockwise and it might loosen up without the tang in place. On the right side it would tend to want to turn clockwise which would tighten.