forums / users are able to reply to messages without given the response to response permission

1. Create a new forum.
2. Add a new topic and set custom permission for students. Set New Response to Yes (checked) and Response to Response to No (unchecked) for the student role.
3. As instructor, start a new thread.
4. Log in as a student and got to Forums.
5. Click the topic title. You should see the option to post a new thread.
6. Click the title of the thread posted by the instructor. You should now be in the thread view and there is no Reply option.
7. Click the title of the thread again to drill down into the message view. You will now be able to see a Reply link.
8. Click the Reply link and post a reply. No error message appears. The Reply icon and link at the message level should not disply if the user does not have the Response to Response permission.