>If Twitter shuts down, you’ll lose your followers. If Facebook shuts down, you’ll lose your friends. For some platforms, it’s not a question of “if”, but “when”. Wouldn't this happen as well if the instance my account was created in shuts down?
It would and it has. In Mastodon-speak, this is called an "extinction event", and I have seen a few of those. Mastodon, however, has already implemented take-out feature where you can download all of your data at any time, including your friend list. It's not perfect, because although you can keep your followee list, your followers don't have an automatic way of knowing where your new presence may have moved to. Also…
If you own your domain name you can have a provider die, and you'll still be able to re import your data on a new provider, assuming you're able to set up a DNS
And that's where you lose most non technical users I guess?