I would be careful of carrot peelings in stocks. The carrot, like most roots tend to rot from the outside in. The peelings you would get from most supermarket carrots are already pretty old (unless you buy the carrots with the tassel still on them) and could easily sour the vegetable flavor of your stock.
I wouldn’t use them just because of the dirt aspect. Carrots are cheap enough that my peelings just go in the compost bin.
It’s never been a problem, but thanks for the heads up. :)