It seems to me that that thread, and hence this one, is misleading on the issue of noise without some clarification.
Because you can't understand it, doesn't make it misleading.
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You see no difference in noise between the two examples shown here or the multiple one's shown on the other thread? Another display issue?
Yes, noise will be lower (but by how much differs from camera to camera) if correctly exposed at a higher ISO than underexposed
Unless
you love non-image forming data, (noise), lower is better. But then if you're OK under exposing your image data too, I suspect you're the kind of photographer (to be kind) that doesn't care much about noise either.
Some of us do. Some of us were professional photographers. Others are just serous about the craft and quality of their images and image data. Some of us believe in GIGO:Garbage In Garbage Out. Some here should stick to in camera JPEGs or cell phones for image capture.
But, noise (and things like posterizsation) will be lowest when correctly exposed at the lowest ISO setting.
Expect when it isn't with respect to ISO and noise as shown and apparently misunderstood by some. I'll refrain from commenting on whatever
posterizsation is
The term "correctly exposed" is of course open to further explanation/interpretation, like ER, ETTR, etc.
Only for those unable to understand how to view a raw Histogram.
AS was outlined in the 2011 post, with the cameras that operate as shown, you've clearly missed the advantages of HIGHER ISO with less noise:
One may use the same aperture and shutter speed (because you are somehow restricted to those settings), it can be advantageous to increase ISO because it can reduce the noise as seen above!Achieving so called "ETTR" through ISO only makes sense when exposure is inadequate. This can occur in many shooting conditions like low light conditions, large DOF requirement, quick action, etc.