That's a pretty hairy situation. Thankfully, Modern technology has enabled us to resolve it.

If I'm shipping anything via BTC, It's being shipped delivery confirmation (signature required, etc). I'd advise the same for all other sellers. To resolve the issue of the item not being what was ordered, Video conferencing allows both the seller and myself to see the item in question.

For large purchases or valuable items, I would advise bringing the mediator into the loop before finalizing the deal, just as a way to be sure everything goes well.

For special cases, I would also be willing to travel, in person, to settle the dispute, but that, obviously, will increase the cost of the service considerably.

The thing about mediation is that it acknowledges that every case is different. There is no universal law which will be able to be applied to every case. Since every case is different, every solution is different, But I won't be satisfied - or paid - until both people are satisfied.

I would also like to point out that anyone who would like to contract for my services beforehand, as a sort of insurance, can do so free of charge. Holding such a contract is a negligible expense on my part.