Traded on reddit /r/GameTrade and initially trade went fine. When I checked back on the gift link, the user had refunded his purchase through Humble which invalidated the gift link. I left him a message to give him time to fix the issue and when I followed up again he had deleted his reddit account and unfriended me. Confirmation of our trade is here .
He went first, all worked out fine. Quick and fast trader.
EDIT: The game was revoked from my steam library, so I recontacted the user on Reddit. He was quick to respond, re-added me within a few hours, apologized and gave me a new key. He explained that he refunded the Yogscast Jingle Jam 2017 bundle because he didn't like the games that he was getting out of them, and forgot about the trades that he made with people. However, I was contacted two days ago by the moderators on /r/GameTrade, asking if I still had his profile because he recently deleted his Reddit account, breaking contact with the other users who had their games revoked.
So, my trade went well (so far), and I will update this again if this changes.
Friendly trader. Thanks. +++rep