We were at the grocery store the other day when we ended up in the same aisle as someone dressed with her face covered, presumably for religious modesty. Emberly spotted her.
It was really pretty endearing and I hope she wasn't offended. We let Emberly know that she should really keep comments about the way people are dressed to herself, just in case it would hurt their feelings. Later we tried explaining that it probably part of the lady's religion to have her face covered, but it was too abstract for her. Politely preserving people's feelings was enough.