I have accidentally closed pull requests several times. I think it is very likely because the "Comment and close PR" button is conveniently located just beside the "Comment" button
A js/alert would probably mitigate this issue.
ASK HN: js/confirm on close PR in Github?
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Re: ASK HN: js/confirm on close PR in Github?
#2Yep, I had the same problem multiple times, all by accident. However chances of this (Ask HN) making it to a GitHub employee are slim. Let's hope for the best.
Perhaps try Twitter next?