I'm not sure there's anything wrong with this as a discussion prompt... Personally, I find it more difficult to respond to a "negative" suggestion (i.e. guarantee a lackluster response) but when you explain how this can work from a TRIZ perspective, it makes sense.
Perhaps to add just a little twist to the directions, re-write comme ca:
What are some things you could say in a discussion prompt that would guarantee a lackluster response from your students?
Be boring! Be verbose! We look forward to your ideas.
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A bit off-topic but ... as I contemplate further what causes lackluster responses, I think about vague, complicated requests that sound like a lot of work. Remember the Final Exam?