Are quote/misquote attribution questions of the "Did X really say quote Y" kind on-topic for Skeptics SE?
I agree with Borror0. Not every instance of a "Did X say Y" type question would be worthy of a skeptical claim, however, in the Marcus Aurelius case is of great notoriety (You will see it all over the internet on facebook, Google+, etc.), yet when I attempted to answer the question, I couldn't find anything that had that quote attributed to him that was dated to prior to 2009 (WikiQuotes says 2010 is the first appearance).
I would say that when I fist saw that quote attributed to him, it did align with other quotes that are attributed to Marcus Aurelius and have documentation. Hence why many people have accepted this new one at face value. I think this may fall into the list of famous posthumous quotes from the likes of Einstein, Twain, Jefferson, etc. Or even the posthumous quatrain from Nostradamus in response to 9/11.
Attribution of the quote to a person is a claim. "This was said by Marcus Aurelius." It's definitively on-topic.
Lit mod here. Unless the question is along the lines of "Was x quote written by y author?" or "Was x quote in y work?" I really couldn't see these being on-topic for literature.
So, to reiterate, unless the quote is associated with a literary work it would be off-topic.