If a transaction was sent in such a way that it could be reversed then that opens up the chance for someone to buy something and then take their money back. Would the receiver be able to spend the coins or would this ability to revoke a transaction prevent that till a point in time.
I don't think I fully understand how this type of transaction works.
Bitcoin transactions are not reversable, but they can be delayed by use of the 'time-lock' feature. Basicly, this prevents the transaction from being included into a block prior to a certain block number, so that the sender can first prove that he has the bitcoin to make the deal in such a way that the seller is willing to give him the product.
There are also the possibility of transaction versions, but this feature requires transaction scripting, which is presently not honored or enabled by any miners due to the possiblity that it's dangerous.