A new account whose name makes the same handle as a deleted account now gets the next free handle, such as okokandrew-1, instead of failing with "Your account could not be created." This applies to every way to sign up: email, Google, Apple, GitHub, LinkedIn and the app.
An email address, or a Google, Apple, GitHub or LinkedIn account, that belonged to an account an administrator deleted cannot be used to sign up again. Sign-up now says so instead of asking you to try again.