I saw this in a local newspaper here. Here is a link to the entire article.
Here is an excerpt. The bold is mine, is that accurate?
"In determining when double-tapping is or is not acceptable for a particular circuit breaker, a simple rule of thumb is to check the design of the connecting hardware at the breaker. If the hardware is specifically shaped to accommodate two separate wires, as with Square D type QO breakers, then the connection is acceptable and should not be cited as double-tapping in a home inspection report. But if the connecting hardware is a simple screw or lug, it is reasonable to assume that the manufacturer of the breaker intended there to be one wire only at the connection. In that case, double-tapping would be the proper disclosure for a home inspector. The only way to connect two circuits to a single breaker in that instance would be by indirect means. The accepted method would be to connect a short wire (known as a “pigtail”) to the breaker and to join the other end of that wire to the two circuit wires with an appropriate connector, such as a wire nut. "