Insignificant
Insignificant becomes a rather specific metaphor specifically for one person in the novel. "And then at last Lady Lufton spoke it out. `She is— insignificant.'" Lady Lufton, as the name by which she is almost always referred suggests, is an aristocratic snob. Insignificant is a metaphor for commonness and its application illustrates that it is comprehensive. It applies to everybody of a lower class regardless of what they may actually contribute to society.
Can't Look Away
Lady Lufton and her son are enjoying a good laugh at an anecdote centered on gossip and humiliation. The son, Ludovic, observes "It would have been like a bull-fight I suppose—horrible to see no doubt, but extremely interesting." This simile is the pre-automobile equivalent of the similar metaphorical image of slowing down when passing a car wreck. It also points out the ingrained psyche of the privileged class.
Matrimonial Fires
An exceptionally long and complex metaphorical image is used to describe the peril of courting. Men are characterized as "absolute moths. They amuse themselves with the light of the beautiful candle, fluttering about...in and out of the flame...till in a rash moment they rush in too near the wick, and then fall...burnt up and reduced to tinder by the consuming fire of matrimony." It is a densely packed metaphor, but basically carries a simple idea. Men who play around with women's expectations of marriage eventually wind up getting outplayed and married.
Friendship
The description of the oddly named Mr. Supplehouse uses metaphor to penetrate into the foundation of his personality. "Mr. Supplehouse felt that he was the master mind there at Gatherum Castle, and that those there were all puppets in his hand. It is such a pleasant thing to feel that one’s friends are puppets, and that the strings are in one’s own possession." The comparison of human beings to mindless puppets whose fate is in the hands of another is a common metaphorical trope related to paranoia, power, and anxiety. This example illustrates that it is hardly a modern concept but goes back at least to the Victorian Age.
Hypocrisy
"Poor Mr. Smith, having been so rudely dragged from his high horse, was never able to mount it again." The metaphor of the high horse in this description reveals that Mr. Smith is a particularly unpleasant hypocrite. The term "high horse" is a metaphor for demonstrably exhibiting an especially smug sense of satisfaction at one's own certainty of superiority. To fall from that horse is a phrase indicating that the person has been revealed as a hypocrite who is guilty of the very things he has been so judgmental about in others.