To determine if your GitHub account has been banned or restricted by a repository or organization, you can look for specific signs. If you are unable to comment, create issues, or perform other actions on a repository, it might indicate that you have been banned from that specific repository or organization. Additionally, if you receive a "404 Not Found" error when trying to access your repositories or profile, it could mean your account has been blocked or restricted, though a "404 Not Found" error can also occur for private repositories that you do not have access to.