From what I could see, knock out and regular attacks do damage to the HP pool. So you could just damage them normally until they are low, and then down them with a non-deadly finishing blow to "not kill".
Question is, what benefit does this provide at the moment? Maybe some storyline choices later on?
role play is the big one. there is also different consequences if you knock out vs kill outright certain people. (I believe, maybe misremembering them) and I tend to follow the damage heavily to within 9 or so hp with outright damage, then switch to knock out. Though it to me defeats the purpose, I'm only going to knock you out, but before that I'm going to try and maim you significantly.
