was playing in my survival world and found this from skeleton drop. I was also able to combine other equipment with an anvil and the different protection enchantment stacked.
MC-143147
Protection enchantment stacks
Resolved
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0
nigel
(Unassigned)
Unconfirmed
Minecraft 19w04b
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Upon testing every other mutually exclusive enchantment, only protection enchantments are now not mutually exclusive. No others are affected.