Shards of Dalaya (a heavily modified Everquest server) did some things really well, and trading is one of those things.
First off, items that are bind on equip can be unbound for a price that is roughly the cost of buying the item from scratch from someone else. So it wasn't any use to sell items that were bound to you because it cost just as much to unbind it, but if you really wanted to trade it to a friend or an alt, you could unbind and do that. You could also dismantle it which made it un-usable, but you could then sell it to merchant for some plat, which was at least a little something - good for when you get an upgrade.
The best thing though is that they have a global auction channel, so it works like the East Commons tunnel where people manually trade, but you can do it even while you are out adventuring or whatever, so you don't need to stand in that tunnel for hours to try to flog an item. Also people followed better etiquette and they actually auction properly. And also, you can have an NPC merchant give you a basic cost for any item, so you can just sell to a merchant if you are in a hurry, or you can use their price as a "price check". So you then /auction Selling a Flashy Whatever Longsword - 50 plat or best offer.
You then start getting tells from people, someone will offer 52, someone else will offer 55, maybe someone who really really wants it will offer 65. Then you do /auction Selling a Flashy Whatever Longsword - 65 plat best offer from Flux.
Then you wait a moment and you do:
/auction Selling a Flashy Whatever Longsword - 65 plat best offer from Flux - going once!
/auction Selling a Flashy Whatever Longsword - 65 plat best offer from Flux - going twice!!!
And usually just before you sell it someone else will come along with a better price, and it can take a few minutes until the bids stop coming in and you sell to the highest bidder. It works great, like a real auction, and it means that people get to manually sell their gear, and people (who are online) get a chance to buy it if they have enough money/determination to buy it. And then you can mail it to them or meet in person. And usually because the mailboxes were in towns, people would just do all their auctioning in towns. You could make this a bit more aesthetically pleasing but the idea I think is great.