Villagers equipped with armor do not change visually.

Using a dispenser to equip a villager with armor does not change its appearance.

To reproduce

Place a dispenser next to a villager. Put a piece of armor into the dispenser. Activate the dispenser. The item will no longer be present in the world, as if the villager has picked it up to equip onto itself. However, the appearance of the villager will not change.