So I had three different Monocles from the Living Story event a while back, a light, medium, and heavy. When I added the medium monocle into my wardrobe, suddenly my heavy and light versions were bound too. The issue with that is that I wasn’t going to use those items, and I’m not sure why the game decided I wanted to. The items weren’t in a stack, it was three unique pieces of armor in three separate bank slots. Hopefully there’s a fix for this, since I was going to give one monocle to a friend and sell the other.
I’d warn anyone with multiples of a valuable skin like the original Halloween ones as well, if you bind one while you have more than one copy present they all become account bound.