The love triangle
Ironically, Deborah accepts Janey in her boarding home before she learns that Janey is probably going to steal the affection of her own crush, Hugo. Deborah is a hard worker whose life of toil has caused her disfigurement and permanent disabilities, but Janey is young and hot, so Hugo prefers her, but the whole thing is ironic, because Deborah has to host them both.
The ironic artist
Whereas most men work by doing a trade or a profession, Hugo finds himself drawn to artistic expression. He goes to the same place as the townsmen for work, but he often stays to sculpt something out of the leftover clay. Is art is an ironic expression of himself, because one might say art is designed to last, but his art is fleeting and private. He doesn't make art for public opinion, but for his own emotional desire to create.
The irony of Deborah's theft
When Deborah steals the wallet of a passerby, that is shocking news to the reader who has probably seen her as a kind old lady or something. The fact that no one would suspect her as a pickpocket makes her rather good at theft, ironically, because no one thinks to accuse her. She confesses her actions though, because she wants to be known. This too is ironic.
The irony of Hugo's imprisonment
Hugo is imprisoned by his relationship to Deborah, literally, which is the ironic opposite of true love. Instead of choosing her, he merely accepts her as a thief, and when she is caught, they both go to jail. Ironically, Deborah caused him a deep amount of suffering, because she committed a crime and gave him money from a stolen wallet. His punishment is ironically severe.
The irony of Hugo's death
The suicide of Hugo goes against the grain of the novel, because everything in the story suggests that he will eventually keep pursuing the young Janey, or else he will realize the quality of Deborah's affections, but instead he succumbs to anguish and dies tragically, killing himself in jail. The irony is that Deborah loses Hugo in the most tragic ways imaginable, by harming him, and then by losing him to suicide.
