"People claim Twitter can't possibly moderate content at scale, except that Twitter makes money at that same scale."
I'm sorry, but is that supposed to be a logical argument? Because it doesn't actually make any sense. Twitter is a platform that allows pretty much anyone with an internet connection to post content. There were, on average, 500 million tweets posted per day last year.
So on one side you have the set of potential content creators, churning out half a billion tweets per day, and that number will almost certainly continue to steadily increase. So, as a company with a set amount of income, and who is beholden to its shareholders, what's your plan to moderate 500 million tweets per day while still turning a reasonable profit?