Gender is not an essential aspect of character development.
This theme is portrayed largely through the irony of pronoun usage in the book. Since the AI don't really understand the need for gender, since they're all computers, essentially, they also don't know the right pronouns, and basically they treat everyone as female by default. The story is not effected by this in any way though, so there seems to be a thematic argument against the essentialist views of gender that have dominated Sci-Fi since the beginning.
AI are humanoid in expression.
This is a hugely speculative fictional device, but it seems that Ancillary Justice is arguing that even among advanced AI, the basic rift between those who seek power and those who seek peace would continue. This seems to indicate a natural law that governs the logic of powerful entities, regardless of the nature of those entities. Also, it's worth mentioning that Breq is an ancillary.
Humans are not the central part of existence.
By focusing on AI characters, (kind of like the movie Her, in fact), the argument here is that human-centrism is unfounded. We have no reason to prefer our own mode of consciousness to any other in existence, which extends to AI, but also to animal life by proxy.
Justice is an abstract concept.
By allowing computers to disagree about the nature of Justice, and by returning to the Platonic question about the nature of justice, the novel showcases that absolute objectivity is just not possible for subjective questions.
Identity is the product of experience, not just programming.
Even ancillaries begin to think and feel as individuals because of point of view an experience in this novel. Berq wants revenge, a notably subjective desire for AI. Also, the various expressions of Anaander Mianaai are a good indication that for Leckie, not even AI would be immune to the human problem of subjectivity.
