I know that this was discussed briefly during the original issue's integration, but I really feel that having the Group mode displayed as a top-level menu is a bad idea. It's one thing to display the current status, but to have it so easily togglable is a bad idea IMO. It's far too easy to accidentally click the groups button as you're doing something else on the page and change the nature of a forum from separate groups into a shared forum with a thousand students.
IMO, this should be swapped with the Edit title button, but it should also have a confirmation. In certain situations (especially forums), changing the groups mode can have problematic consequences - e.g. orphaned discussions, or discussions which people can no longer reply to.