Are you sure this is true? You can frequently see satellites in the dead of night. Further, they show up quite plainly in non-visible wavelengths like radio or infrared even during the day.

This of course only applies to visible light, they will be visible in infrared no matter what.

When can you see satellites in the Earth shadow with visible light?

The parent post said that only observations at dusk and dawn are affected. I'm pointing out that, even at astronomical midnight, large fractions of the sky aren't in earth's shadow. For other wavelengths the shadow is irrelevant, since satellites contaminate data even without the sun's direct illumination.

Well sure, at high latitudes and during certain seasons that may be true for higher altitude LEO satellites (Starlink is fairly low), but if we’re talking corner cases, sometimes the surface of the Earth isn’t in Earth’s shadow at astronomical midnight (land of the midnight sun).

Corner cases don’t really count as “frequent,” however.