Golden Feathers, from the Better Dungeons mod, are crafted using a feather surrounded by 8 Gold Ingots, and can be used to make cloud boots. Golden feathers have a durability of 385. They will negate fall damage while in your inventory, using up some durability, and can be repaired similarly to vanilla tools by crafting one feather with another. They will use up durability even if you are wearing cloud boots.
The durability of a golden feather is used by falling, not by hitting the ground. Falling from a great height into water, which would normally not deal any damage to the player, will still take durability from a golden feather in the inventory.
While falling with a golden feather in your inventory, particles will emit from the player's feet.