How irony and sarcasm are seen in Buddhism? For example, are they considered wrong speech in all ocasions?
For many of us, the most difficult part of practicing right speech lies in how we express our sense of humor. Especially here in America, we're used to getting laughs with exaggeration, sarcasm, group stereotypes, and pure silliness — all classic examples of wrong speech. If people get used to these sorts of careless humor, they stop listening carefully to what we say. In this way, we cheapen our own discourse. Actually, there's enough irony in the state of the world that we don't need to exaggerate or be sarcastic. The greatest humorists are the ones who simply make us look directly at the way things are.
Harsh speech is speech uttered in anger, intended to cause the hearer pain. Such speech can assume different forms, of which we might mention three. One is abusive speech: scolding, reviling, or reproving another angrily with bitter words. A second is insult: hurting another by ascribing to him some offensive quality which detracts from his dignity. A third is sarcasm: speaking to someone in a way which ostensibly lauds him, but with such a tone or twist of phrasing that the ironic intent becomes clear and causes pain.
Buddha himself his speech was full of irony and sarcasm, its all over the pages I have read in the Chinese Classical Sutras. I can recall easily some from my memory:
When criticizing those who practiced the Dharma wrongly but wishing for attainment, he said they were wishing making rice by cooking the sands (煮沙成飯), Surangama Sutra. It was directed to those who didn't conquer sexual desire but wanting any fruition of the practice.
When criticizing another wrong practice, he said using human fece crafting an artwork of sandalwood hoping it gave out the fragrance of sandalwood (人糞刻旃檀形).
Criticizing the Brahmin's Self notion, he said it was like a worm by accident eating out a piece of wood forming pattern looked like a letter, they thought the worm knew language!《大般湼槃經》.
I very much agree with Ven. Thanissaro as quoted by above ChrisW. When someone is full of wisdom his speech is an art of speech of the highest form.