5 9s means 99.999% uptime, which translates to a site only being down for ~0.86 seconds per day. This is the golden standard for online services

I can’t seem to find any information on it, but how hard would if be to host your own Bridgy Fed? I feel a tool like this would ideally be decentralized.

This has happened so many times it must be on purpose. Something like those who come back are likely to be more desperate than those who decide to leave and therefore less likely to get in their way.