I notice there are a number of questions that make it to the subreddit's front page without answer, or worse, a graveyard of deleted answers. Would it be possible to run a weekly thread cataloguing the unanswered questions?
In my imagination, the thread would catalogue the past three weeks separately, then by months up to the last six months, at which point posts would not be answerable. (To be clear, I'm not suggesting we go dig up the last six months of unanswered questions. I am suggesting that, should the thread be maintained for 6+ months, that would be the inevitable conclusion.) I would hope that if a question is answered, someone would post to the thread and the question could be removed, and if a question goes unanswered (or is a graveyard of deleted answers or has a conversation seeking clarification of the question but no answer), someone can post a link for it to be added.
For example, here are a few threads from the week December 25 - 31, 2014:
And here are a couple from July 24-30, 2014:
Time alone does not lead to answered questions. This time of year should be of particular concern for lost questions since many historians have been on holiday.
I would imagine that the day of reflection thread on Sundays can serve this sort of purpose. You can post interesting questions that don't get answers there.