¿Por qué como norma general se suele recomendar "girar" el control de nitidez a 0 y desactivar por completo todo tipo de procesamiento digital de la señal, como son los realce de contorno, super resolución, mejora de borde etc?

Aquí respuestas de obligada lectura si lo que se quiere es aprender

Why you need to turn down your TV's sharpness control - CNET

For those who recommend turning sharpness to 0 - AVS Forum | Home Theater Discussions And Reviews

Yikes, so many posts for such an EASY issue... EASY EASY EASY

OFF is ALWAYS the right setting ALWAYS, 100% of the time.

The issue is that "0" is not always OFF. Sometimes 0 defocuses the image, sometimes 0 does not disable all the sharpening.

The only way to find "OFF" is to use a sharpness evaluation pattern.

Any Sharpness setting that is NOT the "OFF" setting is adding distortion to the image. The Sharpness control for video would be like a distortion control for audio. The only right setting for an audio distortion control would be when there's no added distortion.

Sharpness adds contouring that does not exist in the original image and it does NOT make images look sharper. Some Sharpness settings may defocus the image (or something that looks a lot like defocusing). That's also not in the original image so that's a form of distortion also.

The Sharpness control is STUPID. It is SO stupid that some product engineers leave the control in the user menu so the marketing people stay happy, but the Sharpness control does NOTHING no matter where you set it. Hooray for those guys for doing the right thing.