WordPress.org

Where do I edit my signature

1. Log into WP with author privledges and click the 'Profile' link.
2. Select 'Signature Options' and type in your signature.

Can I control whether the signature is displayed / hidden on a specific post

Yes, at the bottom of the "Write Post" or "Edit Post" screen you can toggle the signature's inclusion for that post.

Where can I request help or additional features

The plugin's homepage is located at FullThrottle Development's Website