Starting from 1.21, it was possible to make enchantments that repaired the enchanted item, using a negative value for the damage_item component.

However, as of 24w33a and up to the most recent snapshot 24w37a, this is no longer possible.

Steps to Reproduce:
1. Load into a world that's a version 1.21 up to 1.21.1, that also has the attached datapack. It contains the enchantment file for one testing:repair_damage_negative_effect.
2. Obtain an item that is within the minecraft:enchantable/durability tag, such as a chestplate or a tool.
3. Damage the enchantment so that it is no longer full durability. Use advanced tooltips if necessary.
4. Enchant the item with the testing:repair_damage_negative_effect enchantment, and hold in in your mainhand as per the enchantment file.
5. Observe that it repairs one durability every 20 ticks, indicated by the slight animation of reholding the item.
6. Now load the world into any version 24w33a and onward.
7. Hold the damaged item in your mainhand and observe.

Expected Result:
The item continues to have one durability point repaired every 20 ticks, like before.

Actual Result:
The item is not repairing itself over time, it remains at it's current durability amount.