The Icelandic Horses in the images are all negatively affected by the bit and the contact on the reins. A horse should have a quiet, soft mouth when ridden properly (no noseband required).
An excerpt from an Eclectic Horseman article:
"That brings up the subject of maintaining a sensitive and soft mouth, which goes back to the school of Naples.
It was then clearly realized that in training a young horse, harsh rein action would occur, either inflicted by the rider, or the self-defense of a young horse, and the sensitivity of the bars would be progressively damaged.
Let's face it, a piece of steel in the mouth that is pulled on unilaterally or on both sides with the connection of the snaffle joint pushing against the palette is no treat.
Also for about 6,000 years all snaffle bits had cheek pieces, so when using one rein, the cheekpiece of the other side prevented the bit from slipping through the mouth and pushed the head in the desired direction.
More recently invented loose ring snaffles are not a step in the right direction."
We should think about this in regard to the Icelandic Horses (islandpferd, cheval islandais, ijslands paard, islanninhevonen, islenskihesturinn) and what the bit does to his mouth when the rider's weight is on the reins.