I think there should be an option to be able to add a discussion, but no reply. By setting the prefs like that, and allowing for Ratings, students would be able to begin their forum experience by posting a "discussion" and then rating his/her peers' discussions without having the distracting option of a reply also.
Our first forum exercise (just to understand what it is all about) is to post an idea to improve the school. When they are done posting their idea, they are to rate other students' ideas with "I totally agree" down to "I totally don't agree," with gradations between. This activity is to teach them how to do ratings.
I've found replies allowed along with the ratings link confuses some of my new Moodle students (all of whom are 12 years old or younger). They lose track what they are looking at.
This idea would not eliminate any current options, but would add an additional new option.
Tim-As far as I know, this is already possible. Or am I missing something?