Singularity Sky is fun SF, but I wouldn't call it particularly rationalist -- it's mainly about the breakdown of hierarchical social structure on exposure to sufficiently advanced technology, which is something that I might expect to be interesting to LWers but isn't directly within the site's ambit. The narrative's clearly on the side of Enlightenment values, technology, and social liberalism, and against rigid hierarchy and Luddism, but you can find those in a lot of places; similarly, the leads' advantage is more cultural and technological than cognitive.

One of the leads does (spoilers:) jbex sbe jung'f vzcyvrq gb or, vs abg n Sevraqyl NV, gura ng yrnfg n abg-haSevraqyl bar, but that side of the plot's not deeply explored.