For example: a "Separate groups" Forum has a lot of posts in it, you change it to "No Groups". What happens? Should all of the posts be combined? Is the "group history" of the posts remembered by Moodle if the Forum is later separated into groups again, and so on...
I've noticed that things get weird if the Forum groups mode is changed when the Forum already has posts in it. We try to inform teachers to "get it right" before making any posts 
For example: a "Separate groups" Forum has a lot of posts in it, you change it to "No Groups". What happens? Should all of the posts be combined? Is the "group history" of the posts remembered by Moodle if the Forum is later separated into groups again, and so on...
For example: a "Separate groups" Forum has a lot of posts in it, you change it to "No Groups". What happens? Should all of the posts be combined? Is the "group history" of the posts remembered by Moodle if the Forum is later separated into groups again, and so on...