For context, I've been wearing an elytra with all protection enchantments at level 32767, Thorns 32767, all water related enchantments at 32767, and feather falling 32767. Here are the effects that I've noticed: Can breathe underwater, water doesn't inhibit movement whatsoever, I take significantly less fall damage (around half as much), I only take half a heart of damage from lava and mobs attacking me, and I still get lit on fire by blazes/flaming arrows. Then, if I also put on a playerhead/mob head with all the same enchantments, here are the differences: Water stuff is still the same, still take half a heart from lava/mobs, still only take about 50% falling damage, but now, I don't get lit on fire from blazes/flaming arrows. Here are my main questions: Why does the elytra reduce fall damage, but adding a mob head doesn't? (it's not because fall damage reduction is capped, if I put on boots in addition to the elytra then fall damage is reduced to about 25%.) Why do I need 2 armor pieces with fire/projectile protection 32767 to be immune to fire? Shouldn't 1 already hit the cap? And third, is it possible to reduce fall damage even further?
As SpiceWeasel said in the comments, landing with an Elytra deals no damage (if you land correctly without hitting anything)
I believe this is because fire protection is random at choosing whether or not the armour absorbs the damage (once per tick), and if the probability of absorbing the damage is 0.5, then that would explain the 2 armour pieces. I believe this because I saw this video (from 5:30~) of Xisumavoid swimming in lava and sometimes it dealt damage, other times not.
To reduce fall damage, I think you can use the
/effect give @p resistance 100 255 true