PEEPS! I accidentally discovered a wicked-cool #mastodon #migration #feature.
Account -> Account Settings -> "Move to a different account" (you can also reach this through old-server.tld/settings/migration
And now, mastodon will autoredirect everything to your new account. So much for the 3 old mastodon accounts, I am redirecting them to this one.
Oh - and you need to add that account as an alias in the new profile prior to doing this (This is an unequivocally good thing - two way proofs that you are the same person and can't be spam linked by someone)