It's - WSB can remain retarded longer than you can remain solvent.
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and sticking to the rules when posting here, we'd be grateful. You've also posted good comments, so that should be doable.
Its meaning has nothing to do with Keynes' quote. It's instead a clever play on words that refers to the recurrent accusation (and subsequent meme) that WSB are a bunch of autists/retards who don't have any idea of what they are doing and thus are doing it entirely wrong, and the defiant reply from the WSB crowd where they state they are ready and able to continue doing it for far longer than what hedge funds, who are throwing rivers of cash at the problem, are able to withstand no matter the cost.