Preservation of specs when downsizing?

I'm thinking what a "good" downscaler should be able to do, and found
one aim which I do not recollect seeing before...

Given a "spec" in the image (a tiny area of high/overblown
brightness) surrounded by large enough "darker" area, it should
remain a "spec" after downsampling. (Applicable also to, e.g.,
bright stars in night sky.)

Likewise for "linear specs" (such as loose individual backlit hair).

I think this may be desirable to happen if the "darker area" is about
3px or more in radius AFTER downscaling. (For smaller areas, the
effect should be proportionally diminished?)

[Without this, bright stars would become dimmer and dimmer when
downsizing ratio increases; similarly (but weakier) for backlit
hair...]

For best result, these specs should be put on a separate layer in the
image. This would simplify editing and/or attenuation of this effect.

Are there simple algorithms for finding such specs? Does existing
software provide something like this?

Thanks,
Ilya