VERY NSFW: Ship of the Line: Forever After Earth which just completed, is a very very smutty 24-chapter crossover between Buffy, Stargate: SG-1, and the author's own original transhumanist fiction. (And in later chapters, characters from other fictional universes like Nanoha and Madoka also contribute).

I'm linking it here, partly because the author is very clearly familiar with the LessWrong community, though I don't know whether he posts here under some different name. Whether I recommend it or not... I recommend it for those who would read R-rated stories, but the plot personally lost me towards the end when characters from more fictional universes started appearing -- perhaps because I wasn't as familiar with those characters, but also I think they just weren't necessary: I think the story would have actually likely been better if it had omitted them altogether and just finished with gur gevb'f zhygv-qrcnegher gb fcernq vzzbegnyvgl npebff gur cynargf bs gur tnynkl.

On my part I enjoyed the depiction of a culture whose members seems almost entirely without any fear of physical harm or physical intimacy either.

TRIGGER WARNINGS for a few depictions of rape. Also that the post-humans in question can't be physically or emotionally harmed by such, causes them to view rapes against them as merely "rude".