i disagree because the person can be evil but the character be good. sure there could be some systems in place so a scam is recognized but that doesn't mean it can be seen at the time. good aligned characters may do scams because there's no retribution on them.
If @Finland was scammed by @FibS then Finland could place a bounty on FibS even if FibS is good. other wise FibS would get away with it unless Finland were to PM a human/demon to kill FibS or post a bounty outside of the game. If Phaethonas could see FibS had a bounty they might reconsider a trade. Now FibS reputation is lowered they'd have to clear the bounty or try to lie about it. If enough people placed a bounty because of the scams then FibS would have to leave and try to scam somewhere else.
People will realize that good aligned people can't have a bounty then they'd start to scam more because there's no retribution.
There are trade ui scams in other games. that last second swap out of an item or change the currency. I've heard about it. In warframe a buyer can PM a seller with the wrong amount of plat (premium currency). sometimes the seller catches it, usually if they have only a few items posted but many don't noticed it till they remove the post from the website.
I've seen Eve have groups that sacrifice a ship with drones to blow up a hauler. the friends warp in and scoop up the goods that survived. A bounty system could be used on all of the members even if they are all in good standing. This actually happened to me a number of years back. I lost 1.5b in 1 hauler.