Description
What It Does
Highlights the items in your inventory that you'll probably want to sell to a vendor. The 'cheapest' item is highlighted in orange, so you can easily decide what to throw away if your bags get too full.
It also adds a recycle icon to merchant windows, allowing you to sell all highlighted items with a single click.
And, as a bonus, it highlights the quest reward that can be sold to a vendor for the most money.
How It Does That
If you sell an item with a character, the item is learned to be trash for that character. If you buyback a sold item item, or drop an item on the 'recycle' button, the item is assumed not to be trash for that character.
If no preference is known for your current character, your other characters are considered. An item is considered trash if more of your other characters consider it trash than not.
If no preference can be determined, then by default, items with gray names are considered trash. Soul-bound items are also considered trash if their tooltips contain red text, which implies your character can't use it.
FAQ
Q: How do I tell it that something is trash?
A: Simply sell the item. It will learn by watching. You can also drag an item onto the recycle icon at a merchant to toggle its state.
Q: How do I tell it that something isn't trash?
A: If the item was accidentally sold, buy it back from the vendor, and it will stop trying to sell it. Otherwise, again, you can drop the item onto the recycle icon at a merchant to toggle its state.