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Is there any work being done on reverse-transactions in bitcoin?
Yes. They just aren't widely implemented yet.
See:
https://en.bitcoin.it/wiki/Contracts#Example_2:_Escrow_and_dispute_mediation
Bitcoin has the added benefit that both sender and recipient can choose in advance who has the power to reverse a transaction in case of a dispute.
This is easily the best answer to the OP. While it is not the same as a reversal (charge-back), it is a escrow system that works with Bitcoin today. It is entirely optional, and only requires that the buyer and seller agree on an arbitrator (and if you can't agree on an arbitrator, you shouldn't be doing business together).
Escrow has some advantages and disadvantages over reversals.
Advantages:
- Funds are released immediately when both parties are satisfied. (E.g. when the buyer receives the goods.)
- After funds are released, seller doesn't have to worry that the funds can be taken away at a later date.
- Parties can agree to change the timing. (E.g. seller can ask the buyer or mediator for an extension if there is a delay in shipping.)
- A good mediator can keep both parties well-informed, decreasing misunderstandings. (Compare to a credit card charge-back, when the seller can be surprised months after the sale.)
- Funds cannot be used by the seller until the escrow is released.
In my opinion, the advantages of escrow completely overwhelm the disadvantages.
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