The Bug:
Horses play armor equipping sounds when their armor item is read from NBT.
If a horse has armor equipped, it'll make noise when you change its NBT data.
Steps to Reproduce:
Summon a tamed horse that has some armor equipped on it by using the command provided below.
/summon minecraft:horse ~2 ~ ~2 {NoAI:1b,Tame:1b,ArmorItem:{id:"minecraft:diamond_horse_armor",Count:1b}}
Modify the horse's NBT data by using the command provided below and listen closely as you do this.
/data merge entity @e[type=minecraft:horse,limit=1,sort=nearest] {FallFlying:1b}
Take note as to whether or not horses play armor equipping sounds when their armor item is read from NBT.
Observed Behavior:
Horses play armor equipping sounds.
Expected Behavior:
Horses would not play armor equipping sounds.
Linked issues
Attachments
Comments
Can confirm in 1.18.1.
Can confirm in 1.18.2.
Can confirm in 1.19.1.
Can confirm in 1.19.2.

Can confirm in 1.19.4
It's just that the command that raises the horse is already causing this bug.
/execute at @e[type=minecraft:horse,sort=nearest,limit=1] as @e[type=minecraft:horse,sort=nearest,limit=1] run data merge entity @s {Motion:[0.0,0.5,0.0]}

affects 23w12a and 23w13a.

I fixed this bug with the vanilla resourcepack and datapack. Attached.🙂

affects 1.20 Pre-release 2

affects 1.20 Pre-release 6

affects 1.20.1 and for 23w35a

affects 1.20.4
I can confirm that this is an issue. Also affects 1.17.1 and relates to MC-123450. The expected behavior would be that the "Horse armor equips" sound doesn't play upon running this command.