Comment by lutusp

> How about stellar mass black holes?

Blank holes aren't dark enough. Because of their accretion disks, they typically stand out from their environments. Also, unlike dark matter, black holes tend to give themselves away by the focal distribution of their masses.

> Black holes fit the definition of dark matter, as they neither emit nor absorb electromagnetic radiation, not in a way that could be detected anyways.

Actually, Hawking radiation explains how black holes eventually evaporate, and the smaller the BH, the higher the Hawking radiation "temperature." This radiation is manifest in observations, and along with the energy emitted by accretion disks, black holes are often very conspicuous.

> Stellar mass black holes have been ruled out ...

Wait, the largest black holes are many millions of times the mass of our sun. Or did you mean only ruled out as a candidate for dark matter?

Another argument against black holes as dark matter is that black holes tend to congregate near the center of galaxies, while by contrast dark matter notoriously distributes itself through the entire volume of a galaxy.

I emphasize these are just counterpoints, not refutations, and black holes might play a part in the dark matter issue.