I don't want to be rude but it is your responsibility to ensure that the person you're trading is the right person. I don't think that steam will ban him because technically the trade you made with him is totally legit. Agin I mean technically not ethically. I also got scammed because I didn't checked his Steamtrades link or another sites link. He got +1 and -8 on here. But If you report him to here they can ban him to use this site with that profile.
you're wrong. Steam doesn't only verify technicalities, they look at all ethical and moral violations too. I had been scammed once like this too and though I didn't get my gun back (because it was my responsibility as you stated), I did get the scammer trade banned. The scammer can be reported for fraud, impersonation in addition to scamming.
Another thing that few know about, when you receive offers from people pretending to be CSGOLOUNGE.COM bots or a steamguard software, you can report them for impersonation too and have them trade banned. Keep in mind that you always have to provide sufficient evidence to back your claims. Video evidence works best as screenshots can be easily manipulated.
Please denounce this motherfucker to Steam. I trade an object with a friend and this person changes his avatar and nickname and cheated me
http://steamcommunity.com/profiles/76561198080342449