Books like Hellspark

This was a smart, complex, strongly characterized far-future science fiction in which diverse human cultures spread across numerous planets. It has nothing to do with Hell or fire, that simply happens to be the name of a culture that is famous for being good at learning others' languages and mores. Our protagonist is from Hellspark and is hired to help determine if a recently discovered avian species is sentient. One of the researchers on the planet has died -- accident or murder? If there is a weakness, it is the actual plot with the mystery, which takes backstage to anthropological and linguistic creativity, but I still found it quite enjoyable to read.