[jweissman]

Definitely an almost amusing overlap between different senses of “singularity”.

Such civilizations might be like “simple germs”, their self-sustaining black hole vessels interacting and stirring things together; perhaps the cores of the most “interesting” galaxies are sentient, waiting for one femto-tech civ to arise from a trillion slime-ball planetoids — to make first Contact...

The more general possibility of “intersecting” reality at right angles has been taken up in a few additional works I can think of: in Count to Infinity and Excession.