Micro.blog adds (tentative) support for moving from Mastodon
Mastodon doesn’t lock you into one instance; you are able to “move” from an account on one instance, to an account on another, taking your followers with you. Behind the scenes, it largely based on ActivityPub. Over on Micro.blog, Manton has used this feature to build a means of moving an account from Mastodon, to Micro.blog (which has some pretty good Fediverse support already), while explaining how it works at a technical level. According to the blog post, moving the other way - Micro.blog to Mastodon - is coming in a future update.
Personally I find this sort of data portability to be rather neat! I really wish more services built in this sort of interoperability.