Error 'INVALID_CROSS_REFERENCE_KEY invalid cross reference id' on export of CaseComment via Data Loader

When exporting CaseComment records using Data Loader in orgs with Self-Service Users, the INVALID_CROSS_REFERENCE_KEY: invalid cross reference id error occurs because the CreatorFullPhotoUrl and CreatorSmallPhotoUrl fields attempt to resolve a photo URL for Self-Service users — who are not standard Salesforce User records. There are two workarounds.

Option 1: Exclude CreatorFullPhotoUrl and CreatorSmallPhotoUrl Fields

When exporting the CaseComment object with Data Loader, do not select the CreatorFullPhotoUrl and CreatorSmallPhotoUrl fields in your field selection. Excluding these two fields from the export eliminates the cross-reference lookup that causes the error.

Option 2: Use Data Export Instead of Data Loader

Alternatively, you can run Data Export from Setup to export CaseComment records. Data Export does not encounter this field-level cross-reference issue.