I’m not sure if this has been addressed, but for group discussions, please consider preventing any students not grouped in that particular group set from posting to the discussion board. Currently if an ungrouped student accesses a group discussion board, they're taken to a discussion board with no other participants where they may choose to post. If the instructor then adds the student to a group, that particular student needs to repost with no access to their previous submission. Currently at our institution, instructors need to unpublish all of the group discussion boards until after the add/drop period when all students can be enrolled in a group, and then publish all discussion boards to avoid errors. This fix would remove this need, and would prevent errors for faculty who don't know or forget the correct process
One solution might be if there was an error message at the bottom of the discussion board with a statement like "You must be enrolled in a group to access this discussion board" for any ungrouped students. For self-enrolled group classes, this would gently force students to enroll in a group before any errors could occur.
And to add to the chaos, when an ungrouped student replies to a discussion board, their post does not go to Speedgrader. So if the instructor is using Speedgrader to grade the discussions, they do not see that student's contribution. This causes problems EVERY SEMESTER.
Simply preventing ungrouped students from posting in a group discussion would help a lot. (Even better would be to also fix the Groups feature, but that's probably for another workspace.)