Failing to set a Discussion Group Set when you really wanted students to reply in groups can have serious, negative consequences, like all students responding to a Discussion prompt you wanted as a group discussion. (I often have combined sections of hundreds of students.) This can occur in Discussions by either not indicating "This is a Group Discussion" or, even if that box is checked, failing to "Select a group category".
If a Group exists in the course and one of these situations exists (no group discussion and/or no group selected), when Saving or Publishing a Discussion, a red-text warning appears saying that a Group exists but that this Discussion is not assigned to any. This warning would be similar to when an impossible date is entered for Due Date, etc. Perhaps the user must click through the warning to save/publish.
