I think it's not clear whether or not tail kinks are genetic, which is why most people don't breed them. There was a morph a few years ago that had a higher incidence of tail kinks, but a gecko can also have a tail kink because of position in the egg or incubation temp, or supplementation issues. Most people feel it's better to be on the safe side and not breed.
Aliza
It's very possible that some tail kinks are and some aren't, but I don't think anyone has proved anything definitively. I'm sure if that's not the case I'll hear about it here pretty soon!
Aliza
As someone that is new to the leo game, I have a rough understanding of genetics in general, be it gecko or anything else...and I personally wouldn't purchase a gecko or any other animal with such an anomaly. That is if I was interested in breeding. The risk is just too great. I could care less if the seller "claims" it is a product of being caught in a deli cup or what ever. I personally wouldn't trust that claim unless I knew this seller very well and could trust them 100%..no offense meant to any one. Just my .02...
Now if you just want a great pet and happen to be searching for a very pretty morph, I see no harm in getting one with a kinked tail. It often reduces the price of said animal making it all the better deal for the purchaser.