Nowadays only the grotesque faces are described, as if these are the most expressive. Beauty is associated with artifice; and the hideous with the good. These days only Saul Bellow allows his good and bad characters to reveal themselves through their faces.
According to Baxter the philosopher Emmanuel Levinas argues that the face has a 'unique physical presence that provokes the subject's obligations to the Other'. I think that means that physical presence of a person's face causes us to feel obliged to acknowledge their existence. It means we cannot easily ignore them (though of course some people determinedly manage this very well).
Baxter says that the way we get most sense of a person these days is through their accessories rather than their face, and the only time we notice even these is when tensions arise, when we fall in love or are threatened or coerced. We also tend to notice more when the dramatic space is limited, and we are forced together. In these situations the face is observed, and hence the fact it is being observed is part of the subtext.
Since it has now become old hat to describe how a person looks may be used as subtext in itself: by using this method we can convey the old-fashioned nature of the subject, perhaps.
Then, when the face is described in these circumstances, it is a strong source of more subtext - for example with a fixed smile, which may contrast effectively with the expression in the eyes.
Baxter concludes that the face is still 'where we are answerable to our emotions and to our obligations.' He says that if a story is about about persons with souls then it cannot do that without the face, which refers back to the statement he makes at the start of the chapter: 'the means by which the soul is usually given away in day-to-day life.' This is a final fascinating chapter of a fascinating book.