I typed up an answer for this, but unfortunately, it seems that the question has already been removed. Judging from OP's reluctance to flag it 1 hour ago and JR's screenshot, I'm guessing it was him. This is disturbing on a moral front. This question was intended to discuss whether the question in question should be flagged. It was not intended for others to flag it without thought. I am disappointed in this outcome, as I would have liked to see the answer to the question, if there was one.
Here was the answer I had:
I wouldn't flag it because it's not a substantial theft. Yes, that is subjective, but there's no ideal way to approach this. It's not creative property; it's merely describing a situation. Think of Wikipedia, which is all released freely and legally permitted to quote without sourcing. Although this is frowned upon socially, there'd be no basis on which to report it. I'd treat this question in the same way, although I am not aware of metafilter's policies.
Additionally, if the question was not answered on another site, and the reader wanted an answer, all he can do is repost it elsewhere. It would be fine if he sourced it, but it would simply add irrelevant information to the post and make people visit another site.
In short, it is always good to create new discussion, and that's all I see here, no mal-intentioned plagiarism. I find that a flag would be frivolous and would halt/remove discussion that may have led somewhere.