Many times I've recieved jewels from other players or in the wild that I can't sell back to the merchants for coin. That's fine, but I would think the bank might be able to. By way of it being like a currency exchange, where you can transfer one type of money (some locales trade jewels instead of coins) into another, gold coins.

We already have a sort of system like this where Speckard in Lower won't buy spell scrolls so you have to go Norma in Upper to sell them.

Also The dwarf in teh bazaar won't buy back items that he just sold you, so lets say I bought a heavy flail, I can't sell it back to him even though he deals specifically with this type of goods.

The book store has a similar problem. I would think that you could buy enchanted books there as well as sell books to her, sadly this is not the case.

And finally, I think the half-drow that sells traps (wont say where he is though so other people can find that person) won't buy back traps that I recovered from areas like the portal or troll quest. I'd like to have those items not marked as stolen since even 'minor spike traps' don't yeild that much gold in teh reselling process to make it a balance issue.

If any of this can be fixed that would be nice.

None of this will be "fixed" since everything you mention is entirely by design. We want an economy that is PC driven as much as possible. I believe some gems can be sold to merchants, though.

Selling traps that you recover would be particularly broken, rogues could make thousands.

I'd just like to add that the Duergar not buying goods he's sold you is proper.

Generally, when a PC sells something, they won't want to buy it right back off of the person they just sold it to, even if they deal specifically in that kind of thing (think Wizard crafting a wand or brewing a potion. Why would they buy something they can make in abundance?).

The same applies for NPCs.

Ladocicea I'd just like to add that the Duergar not buying goods he's sold you is proper.

Generally, when a PC sells something, they won't want to buy it right back off of the person they just sold it to, even if they deal specifically in that kind of thing (think Wizard crafting a wand or brewing a potion. Why would they buy something they can make in abundance?).

The same applies for NPCs.

No. Just realised that would make it possible for players who loot other players to sell the equipment. I guess it's fine the way it is now.

There will never, ever, ever be a way to sell items marked Stolen. The Bioware pricing for all those little worthless trinkets and things is ABSURD.

If you do come across items not marked as stolen, it's always wise to inform DM's about them as well. Every once in awhile things get through, and you'll see that a eye with a single use of slow or something will sell for the max gold, 500, and it's buyback is ~2000. Tagging things as stolen keeps this ridiclious pricing system at bay.