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I am frankly astonished that this question is still open: http://mathoverflow.net/questions/78520/software-for-drawing-diagrams.
So I've voted to close. Since someone has left a comment disagreeing with me, I've started this thread. (My hope is also that this will get it closed all the more quickly.)
I agree on all points.
However, the recent question Double referencing on arXiv is somewhat similar [added clarfication: to me it shares points 1, 2, and 4, not the others; yet these three are to me key-criteria]. (I, as well as at least four others, thought it was off-topic too; but then there was also disagreement, in some sense including from Scott M.)
So, it is certainly good to have a discussion.
[I did however not cast a vote, due to a at least temporary self-restriction.]
For me, the deciding factor is 4. I would have left this question open before tex.SE appeared, because mathematicians' needs in graphics software are pretty different from the world at large. Now, I close questions like this with "This question will get much better answers at tex.stackexchange.com."
I'd leave the arXiv question open, because many people here will know and care about the answer, and there is no better public forum.
Update: it is now closed. Nonetheless, if anyone wishes to explain why they think it should have stayed open, or how with a bit of editing it could have stayed open, can do so here.
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