Re: Clothing Stores with a Hechsher – My daughter loves to shop at a specific women’s clothing store in Boro Park because the owner is not afraid to tell her customers “That looks too tight on you. Try the next size or pick a different style.” She will refuse to sell a dress that is not tznius. (This of course only works when the person tries it on in the store, and when it is for themselves.)
She probably loses a lot of business this way, but that is precisely why my daughter goes there.
It’s not a hechsher, and it is certainly unusual. I suppose any customer buying clothing in any store can ask their Rebbetzin if a dress is tznius enough for them if they cared (and don’t trust themselves to judge it.) You don’t need a hechsher. The food industry is very different, because the buyer can’t know if the ingredients and factory are kosher or not on their own without a hechsher.