steps to repro

1. create a group Y with a few users, make sure that user X is not in the group you have just created
2. edit a permission scheme on a project so that only group Y can add comments
3. go to the issue, make sure that user X cannot make comments
4. whilst on the issue, check the permission helper for user X and the add comments permission. Verify that the permission helper says the user cannot create comments
5. add user X to group Y (this theoretically gives them the right permissions to add comments)
6. go to the issue, make sure that user X can make comments
7. BUG: whilst on the issue, check the permission helper (again). It should say that the user can create issues, however it still says that they cannot.

See attached screenshot.