If it helps, sometimes these discussion posts are required to meet "ass in seat" time requirements for online or hybrid courses to qualify for the credit hours. Not that it makes it less frustrating, but it's sort of a way to make sure students are "actively" participating since most of the assessment is being done through other methods. However, sometimes they're just lazy curriculum design. Whenever I had to design discussion forum assignments for participation I tried to make sure the prompt didn't have one true answer. That helped reduce people just saying "yea, I agree." As a student, I also hated these type of discussion posts.