When you sell an item, it should be removed from your collection

Thanks for this suggestion.  We don't have that feature now, because people could have multiple copies of that game in their collection.  We don't know if that version was the one in their collection or a duplicate they are selling.  

At some point we plan to let people convert a collection item into a "for sale" item, and then those will automatically be removed.

Any updates to this? As selecting to sale my collection item does not utilize anything from my collection listing. Plus,  you can add the same item multiple times in your collection if you should happen to have duplicates.