Cannot mark discussions that require initial post as read

[yihanwu1024]

Summary:

If the instructor chooses to only show replies to those who have posted at least one reply, then after missing the discussion deadline, the unread notification will be impossible to dismiss, so will the "New Activity" prompt on the dashboard throughout the rest of the semester or until the course is over.

Steps to reproduce:

1. Create a discussion post set to only show replies to those who have posted at least one reply.
2. Post a reply.
3. Lock the discussion.
4. Use a student account to look at the dashboard and discussion.

Expected behavior:

The user should at least be given the option to disable this prompt.

Actual behavior:

There is no such option.

Additional notes: