The lack of an account migration idiom on Mastodon really is fatal, it is sincerely a thing that keeps me from recommending Mastodon to people. The http://witches.town evaporation to me was kind of like a disproof of the fediverse and I feel like maybe the fediverse dev community should have treated it as such. There needs to be a way to recover your account, "toots", and follower network if one instance goes away.