Lots of things going on here.
If you were to be scammed what would the punishment be?
The user who scammed you would receive a DNT rank (essentially a market ban) and would not be allowed to trade on Sythe until refunding you and passing a pardon.
Would the scammer have to pay you back?
Only if he decides he wants to return to the market on Sythe.
Would you just be banned from sythe?
Temporarily, yes. Permanently, no. Perm bans are reserved for repeat or especially high-value scammers. Replacing the ban with the DNT rank has led to tens of thousands of dollars in refunds going to scammed users.
Lets say you have a max account and sold for $100. Guy recovers it. What could you do as a seller?
If you're selling an account that you're not the original owner of, you are liable for getting it back for your customer unless you agree to a set of terms that state otherwise. As the seller, you would refund your customer or face a DNT rank being applied to your account.
Any legal things that could happen to the scammer?
Typically no. We've had a few users take legal action against others for particularly large scams and other unconscionable acts. Most scams are low-value enough that it's not worth the hassle of pursuing legal action.
Or would you just need to put in a scammer request for a refund.
Sythe doesn't offer refunds. If you get scammed, you've lost that money. We have a
community repayment fund that helps funnel funds back towards scammed users, but I wouldn't count on that as a source of repayment.