What does それ自体がジョーク mean? Person 1: Person 2: From my understanding the line says that itself is a/the joke but it is not clear to me what is meant by this. I think Person 2 is saying something like "the joke is that you are unable tell jokes" but I am not sure.

Person 1 is saying "Are you saying I am a boring guy who cannot even tell a joke?", bit it's a rhetorical question and he is effectively saying "Of course I can tell jokes". And Person 2 is saying " _That_ is the joke". He is negating what Person 1 is saying, so it implies "The true joke here is that you are saying you can tell jokes".

( basically means "ordinary guy" but here I used "boring guy" because it's used negatively.)