Bona fide
in good faith
Where the phrase comes from
Used across contract, property, and the rules about a purchaser for value without notice. Some statutes define it as honesty in fact. Some also require fair dealing.
What lawyers are pointing at
Bona fide is a finding about how someone acted, made after the facts. It is not a badge you can award yourself in a footer. A purchaser who pays value and does not know of an earlier claim may take the property free of that claim. Someone who knew, or deliberately did not ask a question whose answer was obvious, is in a different position. The phrase fails when it is used as decoration.
The same shape in code
A client that retries a payment with the same idempotency key, and does not relabel the retry as a new order, is acting in good faith toward the ledger. A client that changes the key to force a second charge is not. The header is the evidence. The marketing line is not.
A concrete picture
A person buys a bicycle from a shop, pays the price, and has no reason to think it was stolen. That purchase is the usual picture of a bona fide purchaser. Buying it in an alley for a tenth of the price, with the serial number filed off, is not.