How important is citation to your grey owl when the content involves knowledge that has long been generalized and considered basic within a specialty?
For instance, I am working on a post about the cents measurement in musical tuning. If you take the "perfect fifth" in a Pythagorean scale, which represents a frequency multiple of 3/2 times unison, you get its value in cents when you multiply 1200 times its base-2 logarithm, like so: 1200 times LOG(3/2,2), yielding about 701.955¢. If you take the perfect fifth in 12 equal temperament, which represents a frequency multiple of 2^(7/12) times unison, you get its value in cents the same way: 1200 times LOG(2^(7/12),2), yielding exactly 700¢. Thus the difference between them is a little less than 2¢.
If tuning is not your specialty and you are given to doubts or disputes by nature, you might want citations for all of those facts: the formula for calculating the cents value of an interval from its base-2 logarithm; the multiple of unison that represents a perfect fifth in Pythagorean tuning; the variant perfect fifth in 12 equal temperament; and so forth.
But all of these facts are just givens among the people involved in tuning who quantify musical intervals using the cents measurement. Citing sources for these facts would be an extremely arbitrary procedure, requiring a choice between thousands of sources that one would not normally bother to consult at all. It would be exactly like citing a source for the fact that there are 12 inches in a foot.
So I'm troubled by the prospect that your grey owl might remain out of reach when a post involves facts, customary agreements, or conventions that are "common ground" within a field, but might look to people outside the field like points that ought still to be in contention and that therefore should be supported with citations. Do you think this could sometimes become an issue?
It depends on your target audience. But I absolutely agree that this is a grey area which is a bit open to interpretation. That is also why he is grey :)