Discrepancy in lore (spoilers)

[Vyrerus]

When we're ambushed by the miners at Mount Biran Mines, we do KO the (unnamed) one we're assigned to counter-ambush. When the misunderstanding is resolved, Thaffe asks what happened to their compatriot, and you're implied to have answered that he'll probably be fine. Given Jeryk and Thaffe don't bring it up after that, presumably he was indeed fine, if bruised.

In other words, whether we kill, knock out, heavily injure, or just knock about a bit our opponents is entirely dependent on what the plot requires at the given moment.

EDIT: I think a good general guide (with exceptions) is whether the fight is to the death or to submission.

The miners at Mount Biran don't want (or rather, intend) to kill us, but just "arrest" us. In most of the matches where we leave our opponent alive, our opponent also just wants to make us surrender or concede defeat or just go away, or it's basically a sparring match (eg with the Scions during training). If our opponent wants to actually kill us, then we're more likely to kill them.

Of course, the exceptions to exist, although the ones which come to mind at the moment are when we're in favour of mercy. The Temple Knights who attack us at the beginning of the 50-60 DRK questline were fully intending to kill us, but we left them alive. (Sidurgu went behind our backs and killed them, as a "lesson".) And if the enemy is possessed (Surito at the end of the SCH 30-50 questline, Estinien at the end of the 30-50 questline), we also attack to subdue rather than kill.

So it's entirely possible for the WoL to non-lethally subdue their opponents. Again, the difference is plot convenience.

The WoL in the scene speaks, and Thaffe is shocked, "You "think" he'll be alright?!" and he takes a step back with widened eyes. Jeryk then goes to check on the guy. It's actually a tongue in cheek joke, referencing just how murky us hurting other people in quests actually has been. For most of the game, we never get details on people we hurt. We break them, and they are forgotten.

Jeryk brings the man we knocked around up once more, in the scenes after talking to a drunk Magnus, mentioning, "You'll be glad to know I got our friend home alright, and he'll be just fine. He was just a bit shaken up, was all." Immediately moving onto other matters, incredibly nonchalant. Yet, when we beat his friend up, the guy has a speech bubble, "What are you?!" It makes me wonder if the situation is different in other languages.