A business rule is not triggering for the Comments field on the Candidate Profile.
SAP SuccessFactors Recruiting Management
The comments field is not currently supported for recruiting business rules.
Product Management have confirmed that the standard comments field on the candidate profile is currently not supported for business rules. Rules will not effect this field and onChange rules will not trigger for this field. This is currently expected behavior, if you would like to change this behavior please raise an enhancement request.
2090228 - How to Submit Enhancement Requests for SAP SuccessFactors Products
KBA , LOD-SF-RCM-RUL , Recruiting Rule Issues with MDF Platform , Problem