Erm all bitcoin transactions are public

ALL

If you know someones address then you can go back and check all the transactions.

As for refunds, merchants selling using bitcoin still have to follow law of the land, in most civilised countries there is a "Supply of Goods and Services Act" or equivalent legislation where a customer is entitled to a repair, replacement or refund if the good/service is bad. Buying with bitcoin is no different to buying in cash

You obviously do not understand bitcoin or are confused about some aspects of it.