Throughout the story, the Miller shares a number of exaggerated, didactic thoughts on friendship. These hyperbolic reflections are marked by irony, since his grand ideas and reflections tend to clash directly with his own behavior. However, it is important to note that, because he never intentionally says the opposite of what he means, the Miller isn't using verbal irony. The irony of his words and deeds are lost on him, but it's apparent to the Linnet and to the reader. By linking the Miller's characterization with situational irony and hyperbole, Wilde lays bare the obliviousness of those who justify their exploitation of vulnerable people with the conviction that they are morally or intellectually superior.
The Miller's words and actions are consistently contradictory. In a single sentence, the Linnet states both that the Miller never shares any of his great quantities of food or farm animals with Hans and that nothing makes Hans happier than listening "to all the wonderful things" the Miller says about "the unselfishness of true friendship." In the winter, the Miller and Hans don't see each other because the Miller won't make any material gains by seeing Hans. Since Hans subsists on the products of his garden, he "[suffers] a good deal from cold and hunger" and is "extremely lonely." This is a time when Hans could really use a friend's help, but the Miller claims he is avoiding Hans to prevent him from feeling envy. The hyperbole and irony of the Miller's words is striking, as he both admits to avoiding his friend in a time of need and claims to have his friend's best interests at heart: "I am his best friend, and I will always watch over him."
Another irony is that the Miller actually addresses the discrepancy between words and deeds at a certain point in the story. However, he doesn't view this discrepancy in the same way as the Linnet or the reader. The accepted view tends to be that words unaccompanied by action are empty. After all, as the well-established idiom proclaims, actions speak louder than words. Nevertheless, the Miller claims the exact opposite:
“Lots of people act well," answered the Miller; "but very few people talk well, which shows that talking is much the more difficult thing of the two, and much the finer thing also."
In the Miller's view, speech is worth more than behavior because he believes the former is rarer than the latter. Part of what makes this comment ironic is that the Miller evinces some degree of self-awareness through it. By stating that he values speaking well over acting well, it turns out that the Miller recognizes that his actions do not measure up to his words. However, while this is precisely what makes him a bad friend, he believes it actually makes him a good friend.
Throughout the story, the Miller's actions contradict his claims about caring for Hans. After repeating the idea that true friendship is "quite free from selfishness of any kind," the Miller uses the fact that he has offered Hans a broken wheelbarrow that he doesn't himself need as an excuse to make Hans carry out a long series of tasks for him. These tasks prevent Hans from doing his own work, thoroughly exhaust him, and even bring about his death. The Miller tells Hans at one point that "there is no work so delightful as the work one does for others," yet he never once lifts a finger for anyone but himself. In the end, Hans never receives the much-invoked wheelbarrow from his supposedly devoted friend—he only receives empty words.
Early in the Linnet's story, he describes Hans's garden in great detail. The beauty and purity of this imagery verges on hyperbole, which serves to foreshadow for the reader that, over the course of the story, the garden will likely face the threat of ruin.
After the Linnet's introductory "Once upon a time," he establishes the story's main character as "an honest little fellow named Hans." Although he for the most part seems ordinary and unassuming, Hans's main identifying feature is that he works in his garden every day. According to the Linnet, "there was no garden so lovely as his" in the whole countryside. He goes on to name all the flowers that grow there:
Sweet-Williams grew there, and Gilly-flowers, and Shepherds’-purses, and Fair-maids of France. There were damask Roses, and yellow Roses, lilac Crocuses and gold, purple Violets and white. Columbine and Lady-smock, Marjoram and Wild Basil, the Cowslip and the Flower-de-luce, the Daffodil and the Clove-Pink bloomed or blossomed in their proper order as the months went by, one flower taking another flower’s place, so that there were always beautiful things to look at, and pleasant odours to smell.
The teeming purity of the garden mirrors Hans's innocence, which sets him up to be exploited as the narrative progresses. The overstated perfection of the Linnet's description exaggerates the garden's true nature and, in doing so, subtly foreshadows that something will alter the state of Hans's garden—and, by extension, will impact Hans himself. By including a long list that establishes the garden's abundance and beauty at the start of the story, the Linnet signals to the Water-rat and the reader that this blissful paradise is unlikely to last.