Have there been any instances of people suffering reduced edge grip because of the car profile. I imagine the car tire would be a harder compound as well, how does that effect grip?
"Grip" is an interesting concept. Most of the bikes we ride have more grip, or traction, available than we need under most circumstances. That is, riding a motorcycle on regular roads rarely gets anywhere near the limits of the performance envelope of the tires. If you watch video of bikes on track days, shod with regular m/c tires, you will see what I mean. Generally we sacrifice a lot of wear for traction we don't use or need.
Under some riding conditions it is possible for a tire to lose traction, and slide, but usually hard bits of the bike will ground well before the tire gives up. This is true even of motorcycles with car tires on the rear. If that sounds difficult to believe, look up the video of the Gold Wings at Laguna Seca, and see it for yourself.
Where motorcycle tires are poor is when the surface is wet. That is one condition when a car tire will usually perform better. In that instance, the ability to clear water is more important than grip, and the car tire is simply better at it. Equally, the car tire is better at braking in the wet, something Darksiders have been aware of for a long time.
There are a couple of areas where the m/c tire has an advantage. The first is handling. They steer much more quickly, and with less effort. That is something you either get used to, or you don't. They also weigh less, so they accelerate faster and are easier on the rear suspension.
There are all sorts of reasons given for sticking (sic) with a motorcycle tire. Much of that has to do with the approval of manufacturers and internet experts, neither of whom have done any real testing. Indeed, most manufacturers only really approve of the tires the bike is shipped from the factory wearing, a laughable position but one they stick to.
Virtually all the testing of car tires on a motorcycle is anecdotal. That is it has all been done by tens of thousands of riders who have adopted the practise with no known issues. The beads do not come off the rims. The tires do not come unstuck from the road any more than any other tire, and you do not crash in flames and die (well not, it would seem, from your choice of tire).
Some like it, some don't but there are no known safety issues, just "tut-tutting" from those who have decided it shouldn't be done. Darksiding offers motorcyclists a choice. You give up some things for advantages in other areas. It's a free choice and no one is saying you should do it