The practical problem is, of course, enforcing this prohibition on procreation. Forced sterilisation is difficult to sell and problematic because the subjects might wish to have children with other people. RISUG might be a solution, once it becomes available.

I'm not sure what I think of the fact that everyone is concerned with the genetics of possible offspring in the case of incest, but nobody minds two chronically depressed, highly neurotic people, one of whom has a hereditary autoimmune condition, procreating... (The domain of quantification for the slightly hyperbolic "everyone" and "nobody" here is the general public rather than LW. I suspect that many in this community would, in fact, mind the latter case as well.)