Irony of Herr Spinell
Herr Spinell leads an intricate inner world in his artistic mind. On the contrary to that he appears strange and isolated to the outside world. Frau Kloterjahn is the first person he ever spent time talking to in Einfried. In his letter to Herr Kloterjahn he says that his word is his armor, but when Herr Kloterjahn confronts him about it Herr Spinell puts on an apologetic face and barely any word comes out. If word is his armor, then it didn't prove to be very bulletproof in this instance.
Irony of sunset
Herr Spinell sees sunset as a beautiful phenomena throughout the novella. Nonetheless, in the end sunset is ruined for him because he connects it with Anton Kloterjahn Junior. Things are only beautiful for as long as we associate them with positive emotions, therefore the thing in itself is not the beautiful part but it is the way the thing makes us feel.
Irony of Spinell's letters
Spinell is said to keep writing letters and posting them, but rarely gets any replies. The one time it would have been better if he didn't get any response to a letter, he gets it within a short time.