"Bob (this one)" wrote:
>
> Put some butter out in a covered container
> (glass, glazed ceramic or stainless) for a few days
> and taste it side by side with the stuff in the fridge.

That's not a fair test, because you're comparing
warm to cold. Either test it after letting the
refrigerated stuff come up to room temperature,
or test it after the left-outside-for-a-few-days
stuff has cooled in the refrigerator for several
hours (like overnight).

Temperature can have a huge effect on flavor
perception.