What does it mean when someone is described as having porcelain features?

Good porcelain is white and usually has a translucent appearance. That is, it has a pearlesque quality. So if a person has a porcelain complexion, it has this quality.

On the more defined feature quality, this refers to the delicate features of a fine French porcelain doll. These quality dolls are very dainty, delicate, and exquisitely formed. They are prized for their perfectly molded qualities and the hand painting of the face. To the connoisseur of fine dolls, this is the most prized doll. Therefore the porcelain features of the doll are the comparison for novel writing.