As reported in MDLQA-161, thanks to Teresa Gibbison:

Login as a teacher and create a forum with 'Read tracking for this forum' set to On.
Login as a student and check that read forum posts are tracked and that you have no option to disable the feature.
FAIL

What is happening:
"Don't track unread posts" option still available. User clicks this link & a message states "username is no longer tracking forumname"
User is still actually tracking the forum and unread posts are highlighted - the "Don't track unread posts" option remains available the whole time

What I expect:
The "Don't track unread posts" option is not displayed at all