I've noticed that several Access Review (Certification) reports, take for examnple the "Advanced Access Review Report", include a "Comments" column.
When I run these reports, the "Comments" column isn't populated with data, even when comments have been entered in the certificaftion.
The comments field for the "Advanced Access Review Report" is populated when you enter comments in a "pop-up" during action on the certification worksheet view. For example, if you enable "Require Comments For Approval" when creating the certification, a popup will be presented upon approval of the cert item and any text entered here will be shown in said report. In addition, if you've made the entitlement on the application schema remediation modifiable (select for example), then when you revoke a cert item, a popup will be displayed and any comment entered here will also be shown in the report.
If you open a cert and drill down into an individual identity and click the add comment button, this comment is intended to be displayed only on the certification history for this identity. You can see this comment by going to the Define->Identities page, edit an identity and choose the "History" subtab, Identity Certification History table.