I understand that it may be somehow against the idea of a discussion board, but is it possible to organise a pre-moderation of students' questions?
The (potential) reason is the following. I have a Canvas course in Maths. I may imagine the case when a student, asking a question at the discussion board, reveals (fully or partially) the solution to an exercise. It would be better (for me) to have all students posts/replies on the discussion board 'on hold' by default and I will make the 'eligible' questions visible for all just manually (I do not expect long discussions to be honest).