Maybe this is a good fix to "local channel trading"?

The feature what I'm going to suggest probably doesn't eliminate it 100% but should reduce it a lot in the future. If not, then it's a good feature for trading anyway. I don't know how much this will increase server load but it's like a little query. Okay, here it goes. This has been used in certain online game(s) before:

When you want to sell some items, you drag them to chat bar where you normally write chat text. Now game creates a link to that item and everyone who see that link in trade channel and clicks it, see its full stats just like in trade window or in your inventory when you point some item. However, when you limit this feature only to trading channel, people or at least some of them should realize that trading comes easier, clearer to buyers and therefore more likely produce successful trades if you use trading channel instead local channel. Hopefully the developers read this. I think it might be a good feature to Guild Wars.

Ah then they can't mis-represent the item to try and rip you off........

This is not a bad idea, kinda along the lines of an auction house / bazar / annoucement system.

Another idea probably would be better but it might eat server capacity even more.

Feature adds "Trade box" window which looks exactly same as small inventory or storage. You can put there items you want to sell. Once you are done, go to trade channel, click button "show my trade box" and game sends a link from your trade box to trade channel and everyone who click it, can see your items and look their stats just like in their own inventory. This would reduce text in trade channel because only thing what you can do in trade channel would be that "show my trade box" feature which sends message like "Click to see Zakarr's trade box" or you can make it a bit custom like "Click to see Zakarr's weapons, wands, materials, etc. box" or something else. There would be a delay between two messages from same user so no one can spam their trade box. This would also reduce the unnecessary running between buyer and seller because you can remotely see the items.

Trade box feature would only work in trade channel.

Similar to Anarchy Online (the first idea), I often thought it would work well. Sometimes even attempting to drag items into the chat window...

But I notice an increase in aggressiveness of people using the common channel to sell. I say "<Name>, please use the trade channel," and get replies of "stfu u cant tell me wat 2 do" and the like. This sickens me, and people who use the common channel for trading should not get off so easily, in my opinion. I say have volunteers, and I myself would be willing to do this, sit anywhere for an hour or so and just report (preferrably in-game, so you don't miss more of them..) people who refuse to switch channels. They could recieve a three-day ban, loss of money, or another punishment to discourage trading in the common channel.

They can't have people with the power to report someone, who then gets a ban/loss of money/etc. as that could be abused easily.

I really like this idea and if the servers can handle it, I have an improvement to suggest: A global marketplace, or 3, one for Europe, one for Amerika and one for Korea. Each player who wants to sell something, while in a town, moves the things to his trade box, sets a price for each of them, writes a small description then posts it. Any other player in any town can see the marketplace and browse the various trade boxes. He can buy whatever he likes, giving the amount of money the seller has set. Items to be traded remain in the marketplace even if the seller leaves the town. This way people will be able to do quests and missions and not spend their time haggling for prices. Items are removed from the marketplace when a seller is in a town and removes them himself or he loggs off. Items for trade still occupy space in the normal inventory (so this won't be used as a way to save invetory space) but will be unusuable. The normal trade channel as it is will still serve for those who want to haggle for prices, make auctions, trade items for items, etc.

OP 4 teh win

good idea!

i think making a "town" with only storge units as npc, and ppl that want to trade, go there. You know, like put a dot on the map called marketplace.

I like this idea.
Perhaps to save on badwidth or whatever, when you drag an item to the chat window it just writes the details of the item there and sends it in the trade chanel.