Signatures are designed using fields to populate user details from synchronized data. By default, a signature field is automatically hidden if no data is found to populate it. For example, the signature design below includes a field for mobile telephone number:
If this signature is applied for a user for whom no mobile telephone is present, the entire field (including its m: label) is hidden. This ensures that signatures always look neat and professional, with no odd spacing or gaps.
Check for yourself
The 'hide field if blank' behavior is triggered by the visibility setting for fields. You can check this by clicking the field and then choosing to view visibility properties:
Default behavior for all fields is Hidden if this field is empty, so you never need to worry about missing data. However - if required - you can choose an alternative setting here (for the associated field) here.