These things?
Well...
I don't see them being used in the kitchen, although I guess they could be made to work similar to a Ulu, if you felt like making things difficult.
As for using them to encourage other people to change their minds about a particular course of action? That discussion probably belongs in Practical/Tactical. But I've seen plenty of threads in there go off into the weeds, and get lost. There are just too many unpredictable (and rapidly moving) parts.
One of the few points that people seem to be able to agree on is that training is the most important thing. If you've spent a few hundred hours developing the necessary muscle memory, then you stand as good a chance as anybody of making it through a scenario.
Now. If you want, we can also take a few steps back, and ask "if I want to choose a dedicated self-defense knife (or bladed weapon of some kind), how do the Riddick knives compare to other choices?"
Personally, I figure there's a reason that historical knives and swords have the pointy bit sticking out the front. I would go with something like a Sgian Dubh (because my family is originally Scottish), but that's just a personal preference. There does seem to be some evidence that being able to stab or cut the other guy from farther away is a good idea, so I would say these are not that practical.
