Just trying to figure out what you mean.. Currently the only trades allowed on the forum are in game, so it's all by realm. Here's Doobjanka trade posting rules -
Doobjanka wrote:Sometimes you find a rare pet and you want to make sure it goes to a good home. This is the forum for those kind of transactions. Keep them in in-game currency. Nothing against the Blizzard ToS.
Unfortunately, pets not allowed in here include TCG or Blizzard Store pets. Those posts will be deleted.
So I'd think whatever you're trying to set up it would be the trading forum, no need for a subforum. You're saying if someone has made a thread for your particular realm already, you should just post any trades for that realm in the same thread?
The trading card discussion we had concluded that selling the in game
code for in game gold was not against the TOS, so that's still by realm. (If they did open up actually trading the cards at some point, they could make a subfolder for that. But I don't think that will happen.)