Update (16/08/2023): And just like that, it's back. In a new post on the Diablo 4 forums, community manager Adam Fletcher alerted players that the studio has "re-enabled trade in Diablo IV this evening after a backend fix to address the exploit."
Original story: Hey, nice pain shards you've got there, my friend. Want to trade them for my collection of unfomented wound imps? Well too bad, because Diablo 4 just suspended trading indefinitely while Blizzard tries to get on top of a player-reported bug in the system that lets scallywags and rascals use it to duplicate their gold and items.
In a post to the Diablo 4 forums, a Blizzard community manager posted that the studio has "suspended player trading in Diablo IV until further notice due to a gold and item duplication exploit." There's no real clue as to when that further notice will come, either, but Blizzard says it's "working on a fix to amend this issue" and will let you know once it's flicked the trading button back on.
Be warned, though: The corporation's watchful eye "will continue to monitor this activity to ensure a healthy playing experience for all," and players are reminded that "any account that engages in gold and item duplication exploits will be actioned in accordance with our End User License Agreement."
I've reached out to Blizzard to ask for more information about the scale of the duplication bug and how long the system will be unplugged, and I'll update this piece if I hear back.
If you're anything like me or, apparently, a significant number of people inhabiting the Diablo 4 subreddit, your response to this news can be summed up by the phrase "Diablo 4 has a trading system?" Apparently so! It's pretty restricted—that is, even when it's not literally turned off—meaning you can't trade any of your really cool stuff like legendary and unique gear or your jingling pockets of murmuring obols, but you can trade lower-tier items and gold with other players.
But apparently even that has been a problem, which is why the whole system has been knocked out so Blizzard can figure out how to stop people using it to clone their gold and gear. Perhaps the duping glitch and subsequent shutdown will function as a weird kind of public awareness campaign and more people will make use of it whenever it comes back online. But for now, you'll have to keep your malfeasance tokens to yourself.