EmailHeader triggerUserEmail should be used to send the Email Notifications for the Case Comment records created.

Reference Article:

https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_casecomment.htm

Sample Apex Code:

CaseComment objCaseComment = new CaseComment(
    ParentId = '5003t00001icShAAAU',
    CommentBody = 'Testing Demo'
);
Database.DMLOptions objDMLOptions = new Database.DMLOptions();
objDMLOptions.EmailHeader.triggerUserEmail = true;
objCaseComment.setOptions( 
    objDMLOptions 
);
insert objCaseComment;