I have just tried selling the 'Fine' brigandine I created because I have now crafted fine plate to wear instead. When I transfer the item to the trade row it is immediately stripped of its enchantment and priced as a normal brigandine. I've tried this with the newly enchanted plate and it also loses its powers. Game-created fine equipment does not have this problem. Removing the item from the trade row back to inventory does not restore the enchantment.

 

I have tried this with all the merchants in Copperlane market and it seems to happen 100% of the time.

As far as I know, it happens with every merchant. I'm not sure if it's intended. Few times I've accidentally cleared some of my enchantments clicking the item accidentally. Does anyone know if this is a bug or a feature?

This happens to me too. I can't imagine it's intentional - after all, even with enchantments you can easily sink thousands of coppers into improving your gear. Having all that go up in smoke as soon as you show the item to a trader is just ... I can't see how a game designer would defend that.