In a very limited fashion. Ex: You, a friend, and a random run a strike. At the end, you get your rewards. However, you get a handcannon and your friend gets a pulse rifle. He uses handcannons and you use pulse rifles. Both weapons are better then what you are currently using. You and you friend can trade then. So, trading at the end of an activity to be able to get what you need, yes, if both/all parties agree on the trade. Overall trading amongst everyone in game, no. I think it would create a lot of heartache with new folks who don't really know. "Hey, I'll trade you this amazing weapon for that exotic. You don't want that thing. It sucks. Take mine. Go ahead, it's ok." Thing like that.