Grumpy_Mike:
Running the ATMEGA328 at 16MHz and 3.3V hasn't been a problem for the most part.
Why on earth do you think that manufacturers say these things. It is not for fun. You are operating outside the working spec. The fact that it seems to work now is nether here nor there.
Arduino Buono board
Ah so not a real Arduino then. Just a ropy design.
If I'm not mistaken, the voltage/frequency spec is for the quoted operating temperature, up to 85C. If you don't use it in that hot an environment, you can get away with overclocking it. Ideally, there would be a temperature/frequency/voltage curve to tell you what the xx.xx% reliable operating conditions are for any particular set of dependent variables. That's my guess.
I don't know if the Buono board is inferior in design to the Arduino or not. I'm pretty new to this. But the nice thing about it is that it includes a 3.3/5V switch. Pretty handy. It's on me to use this right and to connect the right voltage components and understand the consequences of putting 5V on a 3.3V system. That's just part of learning. But I don't think a non-real Arduino necessarily translate to a poorly designed Uno.