The best part of Karkat's reproductive ship chart (cus of course a troll from culture with huge pressure to provide genetic material would do a REPRODUCTIVE chart specifically) is that despite finding human concept of incest ridiculous, he still took it into account while writing it down. Simply because humans had it as cultural taboo.

He did it as a mockery of it too, given he didn’t see the issue but was like “YOU IDIOTS, IF YOU HAVE THE CULTURAL TABOO THEN WITH A GROUP OF FOUR THERE’S LITERALLY ONLY A SINGLE WAY THINGS COULD WORK!”

Then everyone disregarded that and just had Lab Babies galore.