Adding a custom date field option for ideas would be useful when tracking ideas that have been revisited by management teams. We would like to track how long its been since an idea has been revisited. Once the idea has been revisited, we would change the date of the custom field to reflect the new date. This field would not be visible on the new idea form but would be on the portal so that the idea submitter could see that their idea has been revisited but would not be able to change the date.
Thank you for your idea. This is currently possible by adding the field to the Ideas and Ideas portal layouts. As long as the field is not included in the Ideas form layout, it will not be editable in the portal.
This article provides more details about how to setup ideas custom fields.