just migrated my account from mastodon.social to infosec.exchange. it was mostly painless BUT:

1. you will lose everyone you're following so be prepared to re-follow manually
2. you may lose some followers i guess if they don't allow following on other instances?
3. you will lose all your toots and need to resetup your profile :((

see instructions here: https://blog.joinmastodon.org/2019/06/how-to-migrate-from-one-server-to-another/