I understand how the forum settings works as you outline above. Here is the timing of the testing that occurred on our site to indicate how improbable it is that all of my course students voluntarily subscribed to this test forum:
- BuddyBoss developer created test forum at 3:52 pm
- Email log indicates that at 4:02 pm all 15 of my course students (including my own student test profile) received an email notification of a new reply created in the test forum
The auto subscribe seemed the most likely culprit. However, after receiving your reply I tried disabling bbPress Notify (no spam) plugin and it resolved the issue. I will contact that plugin author and share his response if it helps others with a similar issue if trying to use that plugin.
Thank you for your input.