> you do your color grading in the camera's original color space
you do your color grading in linear color space (or something that roughly maps to linear color space) is what that actually means. Linear meaning, the exposure of a pixel is supposed to be proportional to the data number, and the exposure is theoretically infinite (since you can have anywhere between 0 and infinite light). For display color space (for photography this is more in line with "print media color space") there is a maximum brightness and minimum brightness, and you have all the numbers to map brightnesses between the two.
The math is a lot cleaner with linear color spaces.
you do your color grading in linear color space (or something that roughly maps to linear color space) is what that actually means. Linear meaning, the exposure of a pixel is supposed to be proportional to the data number, and the exposure is theoretically infinite (since you can have anywhere between 0 and infinite light). For display color space (for photography this is more in line with "print media color space") there is a maximum brightness and minimum brightness, and you have all the numbers to map brightnesses between the two.
The math is a lot cleaner with linear color spaces.