Human moderators.
Each grudgingly uses human moderators to squash the worst of the problems on their platform, and does a terrible job of it. Each underspends on human beings, using contractors without sufficient mental health care to ensure their well-being as they sift through our online sewer pipes.
Google outsources YouTube moderation to third-parties: the Content ID system is a labor shifting device designed to force the labor cost of enforcement outside of Google’s responsibility.
Twitter ended political advertisements rather than spend the human cost required to moderate them, and is now proposing a decentralized platform where Twitter is no longer responsible for content moderation for other platforms.
By doing so, they can continue to act as your “aggregator” of individual (RSS-like) Twitter accounts, so that they can continue showing you ads based on the data they harvest from you and your feeds — while outsourcing responsibility for moderation to others.
This is an effective strategy for increasing profits and if implemented correctly will permit mass layoffs of most of their content moderation workforce. This will also vastly increase the prevalence of abuse, racism, and other societal ills that infect Twitter with its underpowered moderation today.
Props to Twitter for identifying a way to externalize the cost of civility while continuing to profit from the resulting cesspool that will ensue.