By far the best definition I’ve heard for irony is “a juxtaposition of the expected and the unexpected.”
In ironic wordplay, the irony arises because you expect the words to mean one thing, when they can actually be interpreted to mean exactly the opposite. It’s difficult for me to think of a concrete example; situational irony is so much more common. Eg, a fire station burning down is ironic in the extreme, or a person who’s scared of flying finally getting on a plane for the first time only to have the plane crash and kill them.
You also get people doing something ironically; eg, I could call somebody a nigger, and people who know me would know that I’m doing it ironically, because it’s the opposite of the way anyone would expect me to behave. Again, you get expected clashing with opposite and unexpected.
Interpreting “Jesus Christ, you’re delusional” as a addressing Jesus Christ isn’t really ironic, then; it’s just taking it out of context. It’s no more ironic than interpreting “fuck me” as a request when the person speaking actually meant it as a mildly self-deriding profanity.
Of course, interpretation of irony is one of those things that people will argue all day. For example, you could argue that “Jesus Christ, you’re delusional” would be extremely ironic if it were being said by one of Jesus’ disciples, because you could interpret it as them calling Jesus delusional, which is clearly the opposite of the way they actually viewed Jesus. color=black