I disagree 200% with the closing off old threads. Only some of the suggestions are based entirely on their OP. The suggestion gets made and discussed. How would this affect Modders? Adventurers? Forts? Future Play Modes and Suggestions? It gets tweaked. We want new posters to have new ideas on the subject, just not repost old ones.
The whole point is that we want new users to
A: Have an understanding of what the major future arcs are
B: Understand that there are hundreds of forum goers making suggestions and only one programmer
C: Save everyone some time by familiarizing themselves with previous discussions on the topic.
We want old users to
A: Understand just how overwhelming the body of work produced both in the dev notes and in the forums is to first time viewers
B: Understand that new users might not comprehend how big the suggestion pile really is.
C: Understand that 'community justice' in giving new posters a hard time does nothing to manage the community, as the next poster will not be accultured either.
D: Be polite and welcoming.
Problem 1
I think part of the variation is based on length of time here. There's a good bit of churn on this forum. Nobody reads the old posts UNLESS they are searching. So if someone posts an idea that they haven't seen before, they'll start the conversation up again. So for any given idea that's been through a few times, active posters will have seen it between 0 and 5 times. The people who've seen it often are familiar with the discussion, the plusses and minusses, what the difficulties are. Someone who hasn't yet seen it will post (often similar discussions to what was previously had), keeping the post new. In fact there may be users who've seen it before, but haven't seen this variation before.
Problem 2
Another issue is the controversial nature of some of the general themes. Gunpowder and Magic, for instance. There are people who feel that their inclusion would ruin the game and that any developer time spent on them is developer time not spent on features that they themselves (and the large number of players who feel like them) would use. That starts the trend of people labeling any magic thread as being the same as the last, because it's been discussed before, and they've already said they hated it and posted a 6 paragraph rant explanation of why magic is a bad idea, and why do people have to keep bringing it up?
Finally, we've got the complex suggestions. Magic is a good one, so we'll stay there. There are hundreds of different 'this is how magic should work' ideas out there. Almost all of them are excellent ideas on how magic could work in a fantasy world. Since this is a fantasy world simulator, they all make good suggestions. The problem is lose boundaries. One suggestion bleeds into another. Good ideas are posted in related threads that never get applied to other applicable situations. Add to that the fact that people feel the need to push their theme agenda, and you've got a righteous mess on your hands.
Ok, enough crap, here's my suggestions:
Sub-fora for the big boys: Guns and Magic, maybe Technology. Just those 3. You should know if you are suggesting Guns or Magic
Wiki page linked in the intro with the 'common suggestions'. Something with short headers and long on keywords, with a hard 10-20 limit on total number.
How to write a useful suggestion instructions: This is up to Toady, but I would recomend something like 'spellcheck, spellcheck the header again, start general and then give examples, and remember to include modding, adventure and non-dwarven forts.
Wiki the Summaries : Summary threads don't work because they are owned and because they disapear. They rarely offer a balanced overview of the topic, and tend to devolve into ideas threads themselves. Wiki stuff can be edited by anyone, which means suggestions don't need to bulk the thread, and balance can be better maintained.