I am not sure if this is possible in the current API but currently when trading items with other people the items DO NOT stack with other items of same name already in your inventory! Would be nice to have a Auto-Stack AddOn that Auto does it or gives you a Merge button.
From line 121-122 I in my mod I call this (a method that does just that but is intended to consolidate and move things from your inventory to your bank).
From line 121-122 I in my mod I call this (a method that does just that but is intended to consolidate and move things from your inventory to your bank).