After trading, players will have the option to vote the trader's trustworthiness. A player can be voted only 5 times per day.
After receiving upvotes, a green up arrow will appear on a player's profile. Double green up arrows means they are an active trader in the community.
If someone got scammed by a trader, they can downvote them. After a certain amount of downvotes, a red down arrow will appear on their profile. The only way to get rid of this arrow is by gaining upvotes.

https://imgur.com/gallery/TOoFSGC