FWIW, my subjective sense (based only on anecdotal experience) is that many (most?) 21st century uses of the term “truthiness”, including ones by people who credit Colbert with coining the word, do not use it as Colbert intended, and have reanalyzed it as meaning something like “having the quality of being true” or “having qualities suggesting something is probably (although not definitely) true.” The people who use it this way seem to think the “joke” is simply that truthiness is “not really a word”, cf. Bushisms like “misunderestimate”. (Just to be clear, they don’t think truthiness is a Bushism, they just seem to see it as a similar kind of ironic usage of a made up, awkward sounding word.) I haven’t, IRL, heard anybody use truthiness the Colbert way (referring to something one knows or suspects is not true but wishes was true or wants to believe is true), although Googling shows me many articles using it that way. But, maybe I just don’t travel in hip enough circles.