Can you sell steam games you have? I mean those that codes I already used. I saw peeps selling old games here on forum, so I guess it is possible.
No you can not, it's a breach of the terms of service that you signed to use steam. Your no longer buying the game just a licence to play it. It's also why you can't sell your steam account. The refunds thing they did was there concession to change.
What people are selling are Steam gift codes. Whenever you buy a game on Steam, you have the option to "buy for myself" (adds the game to the steam library) or "Buy for someone else" (provides you with a gift code). Many people always choose the 'buy for someone else' option anyway, and just redeem the gift code to their own account if they want to play that game. This gives you the option to sell/give away the gift codes at a later date if you never get around to actually redeeming the code, but is obviously less convenient in terms of seeing what games you have available to play.
