I think it was like this in all Larian games.
On top of DOS1+2 I also played Divine Divinity and Divinity 2.
Its just that you could not kill merchants in some of those games, but they kept sold items forever.
My solution to avoid confusion: switched selling
I sell all equipment to a shop that does not sell equipment and I sell other items to a shop that sells equipment.
So when I go to a weapon shop I know I can ignore everything that is not a weapon, even though the inventory is full of items.
Prof. Dr. Dr. Mad S. Tist
World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already
