From the documentation (https://docs.oracle.com/cloud/latest/db112/SQLRF/sql_elements008.htm):
6. Nonquoted identifiers must begin with an alphabetic character from your database character set. Quoted identifiers can begin with any character.
What do you mean? This is just how Oracle implemented it. If you read the documentation at the link I provided, you'll know. It's not something a plugin can fix.