I dunno', I've been told I did a killer salsa, but that was a while ago.
To me, I equate dance more to footwork drills in fighting.
Depends on whether it's choreographed or not, right?
More accurate to substitute "disabling" for "lethality," although in sword arts lethality is a likely result. But, yes, it IS a salient characteristic of (good) kata. Without it, kata is not martial art - only exercise.
Before I respond to this, I want to say, I'm not trying to inflame the kata mafia or troll this thread. What follows are my opinions.
I think there's a lot of mental and emotional weight (for lack of a better term) that occurs that shapes a person over time who thinks about killing people regularly, and who trains to kill people, particularly if they do so for most of their life. I've seen a lot of people who look literally twice their age over their lifetimes. They carry a lot of stuff around, and it has a physical, mental, and emotional weight to it over time. Death is a big one, whether it's fear of danger (real or imagined) or thinking about killing others (whether likely or very unlikely). I see a lot of value in participating in pretty much all martial arts, but encouraging folks to think of themselves as killers isn't one of them.
This is just my opinion, but I don't think it's healthy and I don't think it's necessary. So, when I see people talk about self defense, as instructors or students, and talk about preparing to kill people, (whether it's discussions like this about kata or just classes in general), or being lethal, or being deadly, those are red flags for me. I personally (and this is just my opinion) think it's bad juju.
To be clear, if you're in a position where you may very well have to kill people, it's something you should prepare for. But even then, I think it has an impact. As a practical example of this, most (or all) police departments put cops on admin leave when involved in a shooting, and the involved officer must generally be cleared by a psychologist to ensure that he or she is mentally prepared and fit to return to full duty.
I also think that if you only (or primarily) do kata, the kata IS the skill. And folks are not routinely injured or killed doing kata. I mean, unless they are careless with a dangerous weapon like a gun or a knife. If you're using a "live blade" what that suggests to me is that you're just making the activity you do a little more dangerous for you, like juggling swords vs clubs. The two are not intrinsically connected. If that makes sense.