Some questions cannot or should not be answered. So we need a way to close questions.
Closed questions may be edited into something answerable. Questions may be closed by mistake. So we need a way to reopen questions.
There’s no way to salvage a question or to learn how to write better questions if you don’t know why your question was rejected. Therefore closing a question must state a reason which is visible to everyone.
We need to have some initial policies around closing. This can be a predefined set of reasons, or some more general guidelines allowing closers to write their own reasons.
Refering to the existing answers when someone asks a question that’s been answered before is essential to distinguish a knowledge repository from a discussion forum. Therefore “duplicate of [link]” must be a close reason.
Who can close? We can start with a co-opted set, or with some simple measure of participation (tag-based?). I don’t think we can let everybody close, even with a voting system.
Not in MVP, but later
I don’t think voting is part of the MVP, but it should come soon after. If we already have voting, that’s fine, but it’s a non-trivial feature that shouldn’t block the first deployment.
Some protection against close/reopen wars beyond flagging.
Fine-tune who can vote to close and how many votes it takes. I think we can go further than SE in taking tag competence into account. The ideal settings probably depend on the community.
Have a process around the selection of close reasons. Something I’d like to try is that all close reasons should link to a meta thread that explains why questions of a certain type get closed, and what askers can do (add details, ask elsewhere, etc.). (Exception: closing as duplicate links to the duplicate, not to meta.) To be determined: what the process is to make a meta thread a close-reason meta thread.
Review queues (for closure and other things). Of all the features that Stack Exchange has implemented, I think that’s one of the most useful.