Account/Opportunity Layout shows "Last Modified By" an inactive user who originally created the org

When automated system updates or package enhancements are deployed to standard page layouts (for example, adding invoices, credit memos, or payments to the Account layout), the system may execute the update using the context of the user who originally created the organization.

As a result, that specific user's name is populated in the Modified By field of the page layout. In scenarios where the original creator has since been deactivated, their name will still appear as the last modifying user.

Note: This behavior is purely administrative and does not indicate any security concern, as no manual modifications or unauthorized actions were performed by the inactive user.