Symptoms
During pre-deployment package validation, K2 Package and Deployment identifies a SharePoint column/field dependency which cannot be resolved via the application's UI. The attached screenshot shows the Missing Reference named Approver Comments (_ModerationComments). The error persists even after the application's "Configure" functionality is used to resolve it.
Diagnoses
The issue was caused by “Require content approval for submitted items” option in the Library Settings > Versioning Settings is set to "no" for the SharePoint list in target environment.
Resolution
Switching this option to “yes” allow the SmartObject to be deployed to the target environment successfully.