Which also begs another question about the lines around 'fake'. If you put a quote next to a picture of someone who didn't say it, is that deceptive? "Well sure, the entire point of 4chan's stunt was to deceive people".

Alright, fine. What if the attribution is just plain mistaken in a misleading way? What if you put an inspirational quote next to someone it applies to, instead of the speaker? If the speaker couldn't possibly have said it, or the quote is famously from someone else, so the goal is comedy? Or the countless pictures misattributing that "...fire inside me..." quote which escaped from Fallout: New Vegas? (Is the deceptiveness different when it's shared as a mistake vs meme vs prank? Can your algorithm tell?)

Twitter's put at least some thought into that, thankfully. They talk about "significantly" altered content and whether it's "shared in a deceptive manner". But good lord is that a fuzzy thing to decide or automate.