Several users voted to close this question, Pressure-dependence of electrolysis voltage, in which the OP asked for help identifying the flaw in an electrochemical perpetual motion machine.

I gather the reason was summarized by Mithoron's comment:

I'm voting to close this question as off-topic because it's rather physics then chemistry.

This makes no sense to me. Thermodynamics is a central part of physical chemistry, and questions about perpetual motion machines (of the form: 'I know thermodynamics says this is impossible, but I can't find the flaw') have played an important role in learning and understanding thermodynamics. Further, since this specific question concerned an electrochemical, rather than mechanical, perpetual motion machine, it seems more appropriate for chemistry.se than physics.se.

I'll add one of my chemical thermodynamics students came up with an osmotic-pressure-based perpetual motion machine, and couldn't find the flaw, so he asked me to explain why it was impossible. I needed to spend a couple of hours on my own thinking about it before I was able to provide him an answer. By the thinking of the users who voted to close the above question, however, my student's question would be deemed off-topic for my course. Yet neither I, nor any of my colleagues who also teach this course, would agree with that view.

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    $\begingroup$ I would see that in a similar context as Are questions about the Ideal Gas Law chemistry? I'd reopen the question. $\endgroup$ – Martin - マーチン Jun 28 '19 at 8:42
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    $\begingroup$ While perhaps the reason is not 'correct', the closing I believe is right. The question asks why the cycle isn't perpetual, and has several errors in logic. On the Physics SE it would also be closed quickly, and rightly so. $\endgroup$ – Jon Custer Jun 28 '19 at 14:49
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    $\begingroup$ @JonCuster, so what would you close it as? We don't have a close reason for "having errors in logic" - closest would be unclear, but I don't think that applies here. $\endgroup$ – orthocresol Jun 29 '19 at 10:59
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    $\begingroup$ @orthocresol - over on Physics it would be “non-mainstream”, an option there since Physics seems to get way more of that type of question. Just because a question doesn’t rigorously fit a close description doesn’t mean it is a good fit for the site, or a good question. ‘Where am I wrong’ and ‘am I right’ are two sides of the same bad question coin. $\endgroup$ – Jon Custer Jun 29 '19 at 15:27
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    $\begingroup$ @JonCuster I think questions of the form 'where am I wrong' (or even where people have a conceptual misunderstanding and don't realize it) can be good questions, if they are asked in a clear manner, and I thought this particular question was clear enough. In addition, you yourself have answered questions of this form, for instance: chemistry.stackexchange.com/questions/111637/… and chemistry.stackexchange.com/questions/63055/… $\endgroup$ – theorist Jun 29 '19 at 15:43
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    $\begingroup$ @Martin-マーチン Yes, in terms of subject matter, that seems to be a reasonable parallel. Though the case you linked involved just a single user making a provocative statement in the comments section. Here, by contrast, we had the more serious action of a group of users voting to close a question..... $\endgroup$ – theorist Jun 30 '19 at 14:33
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    $\begingroup$ .....I don't have the 3k reputation needed to view "Close Votes", but I'm curious if it involves a discussion. If so, I'd be interested to understand the content of that discussion, since it seems surprising to me that a group of experienced reviewers deemed a question about chemical thermodynamics as off-topic for chemistry.se. It's as if a question about the properties or synthesis of high-strength polymers used in airframe construction were deemed 'off-topic because it's aviation not chemistry'. Can you shed some light on this? $\endgroup$ – theorist Jun 30 '19 at 14:33
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    $\begingroup$ @theorist - I confess that I am not a robot, slavishly following specific rules. Glancing at those questions and answers only solidifies to me that the question under discussion just isn’t very good. Sorry. $\endgroup$ – Jon Custer Jun 30 '19 at 14:53
  • $\begingroup$ @theorist Yes it was only the topical parallel, and deeming that such topics are allowed (or at least should be) here. We have occasionally had similar situations, with such custom close votes. Closing is a decision every reviewer has to decide for themselves, but it should generally be more objective than voting. There is no discussion beyond what you see in the comments. (Details: A guide to moderating chem.SE yourself - close voting) The determination what is off-topic should be done on meta (if it's not standard). $\endgroup$ – Martin - マーチン Jul 1 '19 at 7:43
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    $\begingroup$ @JonCuster I'd say that a question not being very good and being off-topic are completely different things, and we have different mechanics how to handle them. Close Votes Aren't Super Downvotes $\endgroup$ – Martin - マーチン Jul 1 '19 at 7:43
  • $\begingroup$ @Martin-マーチン - fair enough. I will point that I neither voted to close nor downvoted, so I'm not really interested in commenting further... $\endgroup$ – Jon Custer Jul 1 '19 at 17:44

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