On paper ?
Word document ?
Keep in mind when threads fail to meet your organizational needs ... it's probably the same for all of us. You don't use xenforo's native structure because important stuff gets lost too easy. If Xenforo is going to innovate and improve online communities ... it will be through solving these "everyday" information needs.
People make duplicate suggestions because it's hard to find old suggestions. PERIOD.
If old suggestions were easy to find ... they wouldn't make duplicate suggestions. PERIOD.
Threads are fine repositories for back and forth banter. As soon as you have a goal (in this case to organize suggestions) .. threads fail. Fail miserably. It's because threads don't have the correct structure to meet the needs of the goal.
Xenforo needs structures other than threads to improve the information experience in online communities.
I look forward to what Xenforo brings to the table when it doesn't hide behind the shield of "But we are just a forum software".