Yes it can damage the pelt and not good for sale.
I believe it to be a pinched nerve or some small spinal problem.
I have a neighbour that had a female with a curly tail, and one day she got stuck between the wall and bed leg.
She was having problems moving her legs after they got her out and took her to the vet.
Exrays showed no breaks and the vet figured she's stained, tore, or pulled muscles trying to get free and should be ok in a few days.
She was, but her really cork screwed tail staightened out. Been straight ever sence.
And they named her Piglet because of the tail, now they have to explain the name, where as before it was very obvious.
There is a thread were Jo ann spoke about it too.
I would not breed a curly tailed chin just incase it was a genetic defect that could be passed on.
It may look cute but how do we know it's not causing them some discomfort, or it could be an injury during birth.
To may unanswered questions to risk it for me.