When "bartering" with the vendor in the druid grove I was handing over my collected trinkets (one party member's inventory at a time you know) and it took me to the 3rd character to see that I was not getting any money in return! I had no idea!
I think this could be fixed by giving a warning when you are "giving a gift" to a trader.
They need to just remove the barter button and create a regular trade interface. When I add something to the shop window it should put the gold into the merchant's side.