Blizzard has suspended player trading in Diablo 4 in the face of a duplication exploit currently threatening the game's in-game economy, and the developer has threatened bans for players who partake of these illicit gains. It's unclear when the function will resume.
Trading items in Diablo 4 occurs in a morally grey area, supported by Blizzard but facilitated by the community. Only a marginally better idea than Diablo 3's disastrous in-game real-money Auction House, it requires inviting a stranger into your party and some mutual trust. These dirty digital deals are arranged on forums or through Discord, adhere to an arcane code of conduct, and scams are commonplace. That was all seemingly fine, but a duplication exploit that allows cunning criminals to amass billions in gold, like the one that took trading offline back in August, is a step too far, and Blizzard is fed up.
The developer ominously reminded players that "any account that engages in gold and item duplication exploits will be actioned in accordance with our End User License Agreement." It later clarified that "players who accidentally traded with a player found using the exploit won't be actioned against."
We'll undoubtedly be using the term "actioned" in future threats, which Blizzard defines in this context as being able to "suspend or revoke your license to use the Platform, or parts, components and single features thereof, if you violate, or assist others in violating, the license limitations set forth below." So, it's banned, or at least suspended.