I got a clothing item that I already had and was wearing, so I tried to destroy the new clothing item but it and the one I was wearing both got destroyed. It has happened multiple times and I am not sure if it is some setting I’m missing or if it is a bug.
When you discard a crafting item, for example, a shovel, the same equipped item will also be discarded.
Here to second this. I had a white head piece in my inventory. Picked up a purple version of the same head piece. Deleted the white one to make room in my inventory, and it deleted the purple one along with it, all in one button press with no prompt. Tested it out with a sword that i had 3 of that I didn’t care about, and the same thing happened
This has happened to me as well
I have found a bug where if you have 2 of the same equipment and discard one it discard them both. Had 2 common staffs and discarded 1 of them and both disappeared. I had 1 common glove in my inventory and an epic glove equipped. Discarded the common glove and the epic glove was discarded too. Dont know if this has been posted yet just putting it out there.
Best to just keep whatever you find in a chest and be careful what you discard. Wouldnt even try to sell stuff you have duplicates of it might have the same effect and sell your purple as well.
When destroying/ discarding an item (1 ITEM !! ) all of the items that are the same as the discarded one will get also discarded/ destroyed. I just discarded a helm now and it also discarded my equipped rare helm … 
When you want to discard just single equipment in the inventory, will cause all the other same equipment be discarded. Maybe you could reproduce this bug no matter where you are I think.
Here is the video I recorded、log files and my dxdiag infomation:
This bug could seriously disturb game experience，fix it please.
Sorry for my bad English and Appreciate for your efforts to the game.
The same happened to me when discarding a club resulting both of them disappears!
When you discard a shovel/axe/pickaxe you discard all of the same items that you have in inventory. Eg I had 2 axes, I discarded 1 and the other also disappeared…
Same here.
I discarded some wildling pants and moments after I noticed my character running around barefoot and bare-assed.
The inventory discarded not only the grey wildling pants from the inventory, but also the blue wildling pants which I had equipped.
Unfortunately it saved already so I couldn’t roll back.
If you discard resources, it automatically takes the max amount, I believe?
Maybe it’s the same (but hidden) when you discard equipment? And it therefore always throws away the max amount of equipment?
Thank you for the report. This is on our radar!