Can I Have an Abandoned or Empty Profile Name?
WordPress.com and related services (including Gravatar) do not reuse usernames.
Even if a profile appears to be deleted or abandoned, comments and interactions from around the web could still be associated with it.
If you believe you own that username on WordPress.com and Gravatar, please reset your WordPress.com account password to gain access to the account. Check your email accounts for the reset instructions email.