Thank you for this thoughtful feedback. I like the ideas you're suggesting here. One of the reasons I wanted to separate duplicate evaluation from other closure (and not even call dupes "closed") is the negative feelings that closure can carry. We certainly don't want askers to feel bullied as sometimes happens Somewhere Else. Will things always be perfect? No, of course not. Can they be a lot better? I think (and hope) so. I hadn't thought of a time-based window before, and I do see how that would reduce tension. Thank you again.

I'm elated to have received such a positive response. It really makes me aware of how I've been feeling, and makes me greatful for the environment that's being cultivated here. Very glad that you think this helpful—I hope that we get some more feedback to try to refine these ideas and figure out the most 'right' formula that we can manage here.

As a note to your first point, an initial draft of this post had a different approach, and did indeed stray more on the side of separating duplicates from closure. If people are interested in that premise, then something I think might be worth considering is differentiating between 'soft' and 'hard' duplicates—the former being questions which share answers, but differ in the content and context of their asking in a way which provides information which is valuable to preserve or offer to an answer-seeker—consider searching for a particular phrasing of a question and struggling to find the 'canonical' answer which has a different phrasing or context—and trying to 'group' or otherwise structure a 'familiy' of answers on the site around a single answer pool. This way, we could try to funnel different approaches to the same core problem into the same (or similar) answer pool. Again, just food for thought—I see the problems here—but I think there might be a good idea lurking in there.

One final thought is that the nature of the issue behind duplicate resolution is a very 'big picture' problem: questions which are asked more specifically than necessary can end up not leaving space for a more general question-answer which would help people who might want to ask a different (also too-specific) question, such that the two questions are seen as duplicates while they both address different contexts of the same (shared) problem or misunderstanding (and likely have detail-incompatible answers for their different details). My point is that this is something which naturally happens in the absence of consideration and almost concerted effort by users to try to ask the 'right' kinds of questions: this might be something we should stress more to new users (although I believe there's a similar sentiment already expressed somewhere in the various Q&A guidelines). I don't think this would make everything perfect—just another thought...not to be sharing too many of those. :)

Your comments make me think of "related questions" or, if that sounds too broad, "question clusters". If people interested in question A probably also want to see question B, we should have some way (that's less ad-hoc than reading comment threads) to create those connections.

I'm not thinking of duplicates as a type of closure at all, though one effect would be similar (no new answers here, because you can go there instead). I want to move them out from under the "close" button entirely. With your idea of soft duplicates or related questions, that'd be even more important -- "soft" / related questions would still accept answers (but also direct your attention to the others), so that's clearly not closure at all.

I like it! How about 'similar questions'? That way, we can keep 'related questions' for what we're used to: questions on a related (but not the same) topic; whereas similar questions are...well, similar questions around the same topic. Naming aside, I think you're bang on—this is an important enough mechanism and dynamic that there should be structure built around supporting it.

I'm not so sure that duplicate-related closure should be abolished (or rather, absent) entirely—but it should certainly be reserved for those select cases where the same question has been asked, i.e. in cases demonstrating low research effort on the part of the author. These are definitely the kind of questions that we should be wanting to 'prune' as unhelpful to the body of informational resources which we're trying to cultivate. This to me is the original intention of duplicate closure as a concept, and what we should be trying to restrict as much as possible without removing it entirely.

Perhaps one way of achieving what you're talking about—and something I'd agree with—is with the use of a closure reason "low research effort/not good question", or similar: the 'implied' closure-by-duplicate for the open-and-shut cases, but with a different name, and separating the sentiments of the two as much as possible. 'Soft' duplicates are then the only thing which we actually call duplicates (in a strange turn)—or perhaps 'related' instead, working under this 'clustering' system. How does that sound?

"Similar" (nice suggestion) and "exact duplicate" seem like useful terms. "Similar" questions would remain answerable; exact duplicates wouldn't. We probably want them to share some workflow; I expect a lot of nominations to start as one and end up as the other. So maybe we present a list of questions that have been suggested as similar, and there's a way to say "that's more than similar, that's an exact dupe" or "yes similar, no not a dupe" (or, for completeness, "no, not similar")? Thinking out loud here -- I'm not sure what the best way is to present this to community members making suggestions, authors, and community members voting for or against.

That sounds about right. I think that the term 'repeat[ed] question' could be useful (to replace '[exact ]duplicate')—both to distance from the established expectations, and because I think it better carries the subtle meaning that this question is repeating another (which is more obviously undesirable), compared to a similar question, which is just that—and harder to conflate. A list of related questions based on keywords (as in Somewhere Else while drafting a question), if that functionality could eventually be added here, could be shown both while writing a question and shown on a side-bar, perhaps? While that may be a little 'noisy', or otherwise undesirable, something like that is I think how we'd present such information (if at all—rather than leave it entirely to users who have seen similar questions before). We could have a very neutral "Something wrong with this question?"-type button in which the options to suggest similar/repeated question reside.

As for questions marked as either, I think that the notice/banner above a question works perfectly well—especially if there's a grace period on the voting, since it only serves to guide users to making the appropriate assessment. I think that it's especially sensible to show the suggestion immediately (rather than wait until voting opens) so that users have that learnt response that such a notice is to provoke their consideration, rather than prompt a decision or (voting-based) input. How does that sound?

I took your proposal and these comments and Lundin's answer and posted an updated proposal.