Calibration in this case isn't about providing "and so everything then looks like it's the same brightness, because it's calibrated" it's about "and so the same modifications can be applied to everything consistently, because it's all calibrated". I.e. just lowering the brightness a bit below the intended value now is impossible. One thing built on a monitor with it's brightness curve undercalibrated and one with its brightness curve overcalibrated will look two different kinds of wrong when shifted by such a transform. That would not be the case with calibrated sources, everything would shift in the same way and you're able to have it look "wrong" (i.e. darker, capped, brighter, whatever) exactly the way you want, consistently.
Taking it to the DPI example, having things built at a standardised DPI isn't about making everything appear the same physical size it's about making everything tuned against a consistent physical size for the exact same reason, default is always intended and your global adjustments are always consistently resulting in the source material being larger than intended or smaller than intended instead of "well, depends how uncalibrated the source was if it's still smaller or larger than intended".
> Calibration in this case isn't about providing "and so everything then looks like it's the same brightness, because it's calibrated" it's about "and so the same modifications can be applied to everything consistently, because it's all calibrated".
You seem to be assuming the commenter you replied to didn't know that. As I understood it, all they were saying is that advice about calibration is useless for people who don't do photo editing, but whose problem is exactly that different windows have such wildly varying brightness that switching from one to another often makes everything look either pitch dark or third-degree-interrogation light in your eyes.
Which category of people do you think there are more of? My bet is on the latter. They need... Well, if you don't want to call it "another kind of calibration", you're free to come up with another term.
Taking it to the DPI example, having things built at a standardised DPI isn't about making everything appear the same physical size it's about making everything tuned against a consistent physical size for the exact same reason, default is always intended and your global adjustments are always consistently resulting in the source material being larger than intended or smaller than intended instead of "well, depends how uncalibrated the source was if it's still smaller or larger than intended".