This is one of the reasons I dislike lore questions so intensely. Lore has a incredibly large scope, much of which can be outside our expertise, especially when it takes into account canon in other forms, such as books or movies.
I agree, though, that having to know if the question is answerable is a horrible metric. I don't see any way around it, though; there is no other control we have on lore questions at all. Without that, any and all lore questions are fair game, no matter how inane or absurd.
But I will expand on my understanding of how we handle lore questions. They are a rather controversial topic, and what I understand our current stance as being is a muddle of compromise between those that want lore questions, and those that want them burned on sight (of which I most certainly am one of).
So, here's how I understand it: Someone asks a lore question. It could be a valid question, or it could be absurd, or whatever. If it's not actually answered in the lore, it's what we commonly refer to as, "Poke the plot hole". Face it; writers make mistakes, and don't always explain everything that happens. Diablo 3 is a mess of them. The point of this control is for those of us who have played the game can go, "Yep, that's not explained at all in the story. Plot hole." We close these questions because they inherently garner speculation, rumors, and other low quality answers, and cannot be definitively answered by playing the game. It's a defense mechanism to keep the site clean, and prevent attempting to prove a negative. The same reasons as we close developer intent questions. Is it ideal? No way. But it's what we got.
What I meant by domain knowledge is that it takes expertise in the game itself to determine if that question is or is not answered by the game. Which is why those that haven't played the game shouldn't vote to close (or reopen), since they don't have the necessary expertise in the domain. For the question being discussed, I am all for closing it. Based on the comments, what's being asked is a plot hole in every sense of the meaning. And I will wholeheartedly endorse it being closed. If there are other Red Alert players, I encourage them to make their own judgement as to the answerability of that question, and vote accordingly. For the record, I haven't voted one way or the other on it.
Lore's a controversial topic; I don't like our current compromise any more than those that want lore questions do. I'd be fine in trusting in the long tail, and allowing Community to delete them if they stick around unanswered, but to my knowledge, Community doesn't delete upvoted questions. So, keeping around questions that can't be answered is just accumulating speculation, rumors, and requires more work on our end to keep the site clean.
TL;DR: If you've played the game, and the question isn't answerable, VTC. If you haven't, leave it alone.