There is also the additional issue of defederation, not just your instance stability. Like if you happen to be one of the 30k users on lemmy.world, or any of the smaller ones that got cut off from Beehaw because you trusted the “it doesn’t matter where you make your account, it’s all shared in the fediverse!” - if there’s a constant risk Gmail decides to block all Hotmail users one day, creating a Gmail account in the first place seems like the safer bet.
And anything you write or upload to Lemmy should be considered permanent, as it immediately spreads throughout all the instances and they actually don’t have to respect edits or removals. And if instances defederate from each other then they simply can’t, as they don’t sync those requests any more - if Lemmy.World decided to defederate from Sopuli, this message would become permanent and I could not do anything about it.
Also, this who saga about the uploaded ID picture.