Irony in Crime and Punishment
Dostoevsky portrays Raskolnikov in an incredibly ironic situation with these two men on either side of the pawnbroker's door. Raskolnikov is, just like Alyona Ivanovna was, hiding and pretending not to be home. This irony compounds on the scene to create an elevated sense of risk and suspense.
A "regular profession" would refer to typical and honest work. However, this line is spoken ironically; the man describes Raskolnikov as a professional pickpocket who pretends to be drunk in order to steal, which is not a typical nor an honest profession.
This question directly addresses Raskolnikov's fears: that in his delirium, he partially confessed to the murder. This statement is an example of dramatic irony because Razumihin doesn't grasp the meaning of this question, but Raskolnikov and the audience do.
Zossimov's words are an example of dramatic irony. He states that Razumihin's theory can't be the truth because it's too melodramatic, or sensationalized. However, the two of them don't know that what Razumihin is saying is the actual truth.
Zametov's statement here is an example of dramatic irony. Readers know that Raskolnikov completely messed up the murder of the pawnbroker; however, Zametov is unaware of Raskolnikov's murder and the truth of this statement. Notice how Raskolnikov takes this quite personally.
Porfiry wants to know what happens to the conscience of people who mistakenly believe themselves extraordinary. Raskolnikov's response is ironic, because he is suffering from the same struggles that he says these people would suffer from: If they have a conscience, they will suffer from the guilt of their crime.
Raskolnikov momentarily comments on the "stupid" repetition of this word. English readers might thing that this word choice is ironic considering that "capital" has meanings associated with capital punishment and capital crimes, such as murder. However, Dostoevsky uses славный in the original Russian, which translates to "glorious" or "nice." The irony then, is more that they are talking about "glorious" things that really are not.
Katerina Ivanovna uses an interesting and ironic metaphor for her life. A ball refers to a very fancy party, often associated with aristocrats and high-class persons. Her life after her youth was far from this, and given what we know about her weakened psyche, it's unclear whether she is being ironic or somewhat sincere.