Death Mark Finish

"Why would putting a monster in deadly count as "killing" something in the first place?"

The warning is because putting an enemy into the finish state removes the Death Mark status from them, so finishing them even immediately afterwards won't count for that training requirement. In addition, once the enemy is in the finish state, they can't have Death Mark applied to them without killing them, so applying it and then killing them becomes impossible. Having the finish rule on is useful for training various "kill with" skills in general, and for Chain Slash in particular having it on allows the player to get an extra hit from an enemy (which leeches more Dorcha to use the skills).

Since it's a common enough situation (having finish rule on for training skills) but also prevents training that method, I placed the warning there so people would know that they need to avoid using that setting in order to train that method.

Ah! I had no idea that deadly removed death mark. I understood it as Deathmark>Deadly wouldn't count as a kill req, which is an obvious statement. Sorry! Perhaps it should just say something like "Death Mark effect gets removed in deadly status, and does not persist past death" or something. That's phrased horribly, but you probably get what I mean.