I might be wrong... so tell me if I am, but does jokes mean cool? :P
yes and no. yes it replaces the word cool meaning 'great/fun/funny/fantastic/nifty,' and when John Green first proposed using it, he had (jokingly) suggested it could replace it when talking about temperature, but the point from the beginning wasn't just to have an inside joke (pun intended) but to actually be subversive, to take something intended as an insult and make it awesome. it also works well in this way for nerd(fighters) as we usually aren't cool meaning popular.