Hey, I'm the person who got scammed. Here is the story of exactly what happened:
Okay, it's a long story, but I am going to try to cover as many details as possible.
I originally replied to this (http://www.reddit.com/r/softwareswap/comments/2hwmuw/h_paypal_w_borderlands_presequel_key_x2/) thread on reddit, offering to trade user /u/dubbykinz a Borderlands: The Pre-Sequel code for a copy of Alien: Isolation. My reddit username is /u/Phib1618. /u/dubbykinz declined the trade, but I later received a message from user /u/SchmuckTen on reddit, offering to trade me Alien:Isolation for the code. We arranged and met on Steam. I gave him the benefit of the doubt because I looked up his steam name on steamrep and it led me to this profile: http://steamrep.com/?id=76561198062619868.
Everything looked in order, so I sent him the code and waited for him to gift me Alien:Isolation. Unfortunately, this never happened. He simply blocked me. I contacted the user he was imitating (OP of this thread) and told him that someone was scamming with his username. We worked together and were able to find that he has scammed multiple people (link to other scammed persons: http://www.reddit.com/r/BitMarket/comments/2d6q97/scammer_two_days_ago_i_was_ripped_off_by/ and http://www.reddit.com/r/giftcardexchange/comments/1wqwb9/trading_confirmation_thread_post_here_when_youve/chxp0h0?context=3) It also appears that this same user has been impersonating this person (https://steamcommunity.com/id/Foxhack) in order to scam people.
Here is an imgur album of the whole encounter, made up of screenshots from the video I captured of the whole thing.
It's mostly my fault for not researching this bastard before trading with him,
but hopefully my experience can help keep this asshat from scamming anyone else.
A user on steam contacted me today letting me know that I may have an impersonator. I searched steam and found a private profile with the same avatar and username. Here is the profile: http://steamcommunity.com/profiles/76561198139392415
I've reported the profile to steam. Please be careful when trading. I'm not a huge trader with lots of rep, but there are some low people out there looking to take advantage.