Issue Summary

When deleting a project role, Jira verifies if the role is being used, and it returns a message similar to the following:

This project role is not associated with any notification schemes, permission schemes, issue security schemes or workflows.

However, it doesn't check if the role is being used to restrict comments, so the end-user may delete a project role that has multiple comments restricted to it, without any validation/warning, resulting in losing access to those comments: 

If a project role has been used to specify who can view a comment, deleting the project role will mean that no one can see that comment any more.

Steps to Reproduce

1. Create a new project role
2. Use it to restrict comments in any given project
3. Delete this role
4. Notice that no validation/warning messages related to comments are shown
5. After the role is deleted, you'll not be able to access any of the restricted comments, and this is irreversible, the comments are effectively inaccessible

Suggestion

It would be great to have any sort of validation/warning if the project role has any comment associated with it, avoiding undesired loss of data. 

Workaround

Contacting Atlassian Support to fix the data inconsistency left (orphaned role ID in the visibility setting of the comments).