The Lunarian Lirion is both a gourmet and a gourmand. (p. 74)
Falaire knows of Rapa Nui. (p. 128) I didn't - although, of course, I recognize the name "Easter Island."
The Lunarian secret society has an appropriate name, the Scaine Croi in Lunarian, the Loose Knife in Anglo. The conspirators cleverly give this name a literal meaning in order to entrap a pilot for their anti-matter hijack.
Within the Solar System, we are used to differentiating the inner planets from the outer planets with the asteroids between. Beyond that, we usually think, are interstellar space and other planetary systems but Poul Anderson opens up a whole new realm: the cybercosm reigns among the inner planets whereas Lunarians, adapted to live on the Moon, colonize Proserpina in the Kuiper Belt.
Anderson's contributions to science fiction remained original and creative right to the end of his long career.