Berry was innocent, even though evidence looked the other way.
This is a straightforward demonstration of what irony is designed to teach as a literary tool: That things are not always what they seem at first glance. A butler allegedly steals a bunch of money and puts it in his bank account—it looks at first glance like he's guilty. But when Maurice receives a letter from an old friend who owns up to the theft, the reader learns what Berry knew all along—he really was innocent the whole time.
The irony of Fannie's decision.
Fannie, in order to do what is best for the family, is forced to leave Berry behind to try and find a new home base. Back down South, the white people are extremely prejudiced against her, and the Black community also rejects her, saying that since her husband worked for a powerful white man, that they were part of the problem. But ultimately, this left Fannie in a position where, although she technically decides to leave Berry, she is only doing what is literally necessary for them to earn money—no one will hire her.
The irony of Kitty's profession.
Kitty's job looks good on the surface; by performing for wealthy men, she can earn a very good salary by working in clubs, but that means that she has to make peace with an essential dilemma of her situation—that she can only support herself by allowing men to use her as an object. One interesting essay idea might be to compare Kitty's ironic job as a dancer and waitress to Berry's own job as a servant to wealthy plantation owners.
Joe's ironic addiction.
Words cannot capture the irony of alcohol addiction. The experience of getting drunk trains a person's body to want to drink when they feel upset, but for a person like Joe, that quickly leads to full blown chemical dependency. And, as Joe demonstrates in his drunken panic attack when he turned violent and killed his girlfriend for trying to break up with him, drunk people don't make very good decisions sometimes, so Joe's use of alcohol literally worsens his life as badly as anything could have.
The irony of violence.
When Kitty marries to a wealthy suitor, she unknowingly commits herself to a fate of slavery. Even though she isn't a technical slave, she is a kept housewife who is "kept in line" so to speak by an abusive man who uses abuse terroristically, to control her. This is not unlike Joe who is also violent (even murderous). The irony here is that people who are in desperate need of social acceptance and hope often become violent, which is not a good way of fixing any of those emotional problems.
