Twitter unified the verification mark for celebrity accounts and accounts whose owners pay a subscription for authentication. The message "This account is verified because it is subscribed to Twitter Blue or is an old verified account" now appears when you click on the blue verification mark.
Under the new rules, it will be impossible to quickly determine the difference between old-verified accounts belonging to public figures such as former US President Barack Obama, and those of users who pay a monthly subscription for a blue tick and reduce the ads that appear on their pages.