Still present in 20w20b. I'd like to add that the armor re-appears when leaving/re-joining the world on Singleplayer, or simply removing and re-equipping the armor from the horse's inventory.
Brian Jensen
Still present in 20w20b. I'd like to add that the armor re-appears when leaving/re-joining the world on Singleplayer, or simply removing and re-equipping the armor from the horse's inventory.