When combining a diamond armor, tool or weapon with netherite using a netherite upgrade smithing template, the resulting item won't inherit the smithing template rarity, Uncommon.
In the same way, applying an armor trim to any gear from a smithing template such as Silence won't inherit said trim rarity color, in this case Epic.
According to the changelog:
Any item or block which can be crafted must inherit the highest rarity of its crafting ingredients.
While this is not "crafting" per se (as in, not in the crafting the table), it could be still considered as an item "crafted" in the smithing table, using 3 items as ingredients which are then consumed.
How to reproduce
Get a netherite upgrade template, a netherite ingot and any diamond gear.
Notice how the template has uncommon rarity.
Combine them all in a smithing table to get a netherite gear.
Notice how the crafted netherite gear doesn't inherit the template's uncommon rarity.
Expected result
The resulting item would inherit the rarity of the template or material. The netherite gear would have uncommon rarity.
Observed result
The crafted netherite gear has common rarity.
Can confirm:
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