I had a question from more than a year ago (Aug 2011) here, which was upvoted 5 times and favourite twice. There exists a high quality (+12) and accepted answer on this question.
In the last couple of days, it has received another random upvote (I assume another reader must have had the same question, found mine, and upvoted it), and then shortly after that it was closed as "exact duplicate" by five low-reputation members. By low rep I mean that a few of them only just barely above the 3000 rep required to cast close votes, and each of them is below the 10k required to see it in the closure queue using the 10k tools.
It wouldn't bother me having a question closed as duplicate normally but in this case the "exact duplicate" is a quite different (but similar sounding) question, really - it's about returning values from other threads not necessarily about the "return value" of the thread target. The accepted answer on my question contains useful information for future readers which is not present in the alleged duplicate.
How does this happen? Did the upvote place it in some sort of recent activity area where it received increased visibility, and then one close vote snowballed? I know that when I first gained the privilege at 3000 rep, the first thing I did was cruise along looking for a crappy question to try and close, just to "test out" my new powers! :) But I can see this becoming a problem in future - with the increased popularity of SO, we can get arbitrarily many members eager to close something whilst the number of close votes needed remains fixed at 5.
I have left a comment and voted to reopen the question, is this an appropriate and sufficient course of action or should I also flag it for moderator attention?