Reading this thread, and then checking my email I notice:
- When a default signature is selected for an account, it will show when creating a new message
- When creating a new message, signature is set to 'none', while it sets the default signature in the message body
- When selecting a signature from the drop down in the new message, it will add it to the bottom, effectively adding a second signature
- When selecting none in the drop down, it removes the second added signature while leaving in place the original.
- Setting signature to random, it will show signature in the drop down of new message, but when set to none it will not remove it. When changing from none to signature, it will add a second signature again.
This is clearly a bug, where a default signature can and will be added to a message, but the program not actually registering a signature is used and added to the message.