A single instance of a self-hosted chat application would also result in unbounded hours investigating some obscure bug that affects 1 in 100,000 deployments, e

A single instance of a self-hosted chat application would also result in unbounded hours investigating some obscure bug that affects 1 in 100,000 deployments, etc; while the developers don't know because they don't have enough ability to remotely dig in and investigate. Self hosting is not a pancea and I would not think it would be more reliable. There's also limited reason why you really want your servers in your city, 5ms of latency savings isn't it,instead of economies of scale in large datacentres with good network uplinks and centralized reliability teams.