The summary of the abstract, by ChatGPT:

The intersubjectivity collapse refers to the breakdown of social and cultural norms in a civilization due to the proliferation of minds of different types and subjectivities that cannot communicate or coexist.

This will lead to conflicts and power imbalances, and make it difficult or impossible predict the actions of others.

It's likely to occur in any society that significantly modifies its own minds or develops artificial intelligence, due to the vast range of potential mind designs.

To mitigate this risk, it's necessary to anticipate it by developing strategies for managing diversity of minds and working on imagining how to cooperate in a civilization of very different types of minds.