I don't think I'm thinking clearly at the moment, but it occurred to me that splitting the soul is based around the act of murder from the murderer's perspective. This makes me wonder if it would actually require a death to split the soul, rather than the would-be murderer believing that they're deliberately killing someone.

If it's the mental process, rather than the actual killing, that strikes me as a potential avenue for slightly more ethical horcrux creation. The details of the horcrux creation ritual might contradict this, or it really does have to be an actual murder. Even if it's an option, I imagine it'd still be a pretty serious turnoff, though maybe there are enough useful mental magics to pull it off and still end with someone who values human life.