I've heard it mentioned often about BF babies' skin. And I've just found this on Dr. Sears' website https://www.askdrsears.com/html/2/T020400.asp Thought the other points were great to note too!
BREASTFED BABIES HAVE NICER SKIN
Many pediatricians who have developed a keen eye and sense of touch over years of examining babies report that they can often tell by the look and feel of an infant's skin whether or not the baby is breastfed or formula-fed. The skin of a breastfed baby often has a softer, smoother feel. There is also less delineation between where the fat under the skin ends and the underlying muscle begins. The skin of formula-fed babies tends to be rougher with dry, often sandpaper-like, patches. Breastfed babies feel more solid. Researchers report that the subcutaneous fat in breast and formula-fed infants actually has a different composition.