Bungie,
If you introduced player trading, you would make many gamers a lot happier due to the fact that this game is based on luck and some people just aren't that lucky. People who have finished the game would have a new reason to play because now they can get stuff that they couldn't manage to before, therefore more playing time on destiny and then more recommendations to destiny which eventually leads to more money. All in all, I think it is pretty clear what you should do
Thanks
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Everyone would have what they want within the first week of trading so there will never be trading