Permanent exceptions to validation rules can be added to whitelists. Whitelisting is restricted to authoring permission.
Whitelisting a concept is easy: just right-click on the reported item in the Validation Issues View and select the Add to whitelist... option.
Whitelisted components are displayed in the Whitelists View. The Reporter column shows which user whitelisted the component.
When someone adds or removes an item from the Whitelist, the views are updated for all users on the same branch. After running another validation, the whitelisted component will not appear again among validation issues until someone removes them from the Whitelist.
When someone creates and activates a new task, the Validation Issues View becomes empty, but the Whitelists View would still have the previously defined exceptions. If a user whitelists something while on a task branch, the newly whitelisted components will automatically be merged and won't be displayed in the validation issues view on the main branch either.
To remove a component from the whitelist, right-click on the component and select Remove from whitelist... option.
