I think you misunderstood his point (and mine). There are usually much better ways to support availability and durability than to have multiple simultaneous write servers. On the contrary, having multiple write servers is usually worse for availability and durability because of the complexity.

For example, look at how Google Cloud SQL's aptly name "High Availability" configuration supports high availability: 1 primary and 1 standby. The standby is synced to the primary, and the roles are switched if a failover occurs.