Also I have never used Steam. From what I read: these are not CD keys or something, right? These are sent as gift with that trading system and cannot ("really") be reversed, right? Thanks.
Not true at all. The advantage of doing an in game trade rather than getting redeemable CD keys is that if the purchase is found to be fraudulent then Steam will reverse the trade meaning your not worse off. Except in this case, since you traded with BTC rather than in game items Steam will just remove them from your account and possibly ban it if it thinks you are an alt account. In effect, it offers you no different protection at all.
Thank you for correcting.
That was the first thing I found, but was indeed wrong. I searched after that post and figured that the game will be removed and account will be blocked if the payment of the trade/gift is reversed. (I don't care about my account though as I don't have other games.)
So when I saw that, I decided to only trade if somehow he had more trust that a bitcointalk newbie. And I figured (based on his steam profile/comments and googleing on his username) that he did do at least hundreds of trades, going back from 2012. So in the end I traded because of that, even though like you said, there is definitely still a risk.
Thanks for making it clear for others. Personally I still took the gamble for 50% off
![Cheesy](https://bitcointalk.org/Smileys/default/cheesy.gif)
but others will have to decide for them own
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
it is indeed not without risk.