No, that won't happen. Even if you post proof to back up your claims of that user being a scammer, admins won't ban him. The community can tag him as a scammer though to warn others not to deal with him ever again.

Why do you think Legendary members can help you? I am a legendary member and I can't help you get your money back or have the user banned.

No one is going to hold your hand and tell you what to do. You have to learn that yourself. It's your job to know who you are dealing with, not anyone else's. If it were up to me, scammers would be banned, however, that is not the case. So be careful and vigilant and don't do things that you will later regret.

Then you made a mistake of trusting the wrong person. What you believe is irrelevant and doesn't change what this forum is.   

I would say the escrow agent (whoever he is) acted professionally and accordingly. Whatever keys you were trying to buy probably shouldn't have been bought/sold here in the first place. Buy it from the official sources and not from some unknown person with 1 post. If you want to partake in illegal activities, be prepared to face the consequences and be scammed. You don't go crying to the police that your drug dealer scammed you when you wanted to buy some heroin for your friends. When you attempt to purchase keys (for a software probably) that might have been obtained illegally, you don't come here crying what an awful place this is.

The forum, just like Bitcoin, gives you the freedom to make your own decisions. You made the wrong one. All you can do now is post whatever proof you have and minimize the alleged scammer's chancers of scamming someone again.