Dear gods, the Language Police are never around when you want them
IRONY: 1. The use of words to convey a meaning that is the opposite of its literal meaning; ex.: The irony of her reply, “How nice!” when I said I had to work all weekend.
2. Literary use:
A. A technique of indicating, as through character or plot development, an intention or attitude opposite to that which is actually or ostensibly stated.
B. (esp. in contemporary writing) A manner of organizing a work so as to give full expression to contradictory or complementary impulses, attitudes, etc., esp. as a means of indicating detachment from a subject, theme, or emotion.
3. An outcome of events contrary to what was, or might have been, expected.
4. The incongruity of this.
5. An objectively sardonic style of speech or writing.
6. An objectively or humorously sardonic utterance, disposition, quality, etc.
COINCIDENCE: 1. A striking occurrence of two or more events at one time apparently by mere chance: Our meeting in Venice was pure coincidence.
2. The condition or fact of coinciding.
3. An instance of this.
Irony deals with opposites; it has nothing to do with coincidence. If two baseball players from the same hometown, on different teams, receive the same uniform number, it is not ironic. It is a coincidence. If Barry Bonds attains lifetime statistics identical to his father’s it will not be ironic. It will be a coincidence. Irony is "a state of affairs that is the reverse of what was to be expected; a result opposite to and in mockery of the appropriate result." For instance:
* If a diabetic, on his way to buy insulin, is killed by a runaway truck, he is the victim of an accident. If the truck was delivering sugar, he is the victim of an oddly poetic coincidence. But if the truck was delivering insulin, ah! Then he is the victim of an irony.
* If a Kurd, after surviving bloody battle with Saddam Hussein’s army and a long, difficult escape through the mountains, is crushed and killed by a parachute drop of humanitarian aid, that, my friend, is irony writ large.
* Darryl Stingley, the pro football player, was paralyzed after a brutal hit by Jack Tatum. Now Darryl Stingley’s son plays football, and if the son should become paralyzed while playing, it will not be ironic. It will be coincidental. If Darryl Stingley’s son paralyzes someone else, that will be closer to ironic. If he paralyzes Jack Tatum’s son that will be precisely ironic. - George Carlin
It's not that difficult to understand, people.