The user https://stackoverflow.com/users/12923651/polcott is very excited about their "insight" about an error in the proof of the Halting problem, and so they would like to share it with everyone:

In some communities, it was already made clear that people are not interested in this insight (there are also older similar posts and deleted posts). According to my real-life experience, this behavior is classified as spam (maybe even harassment). According to https://meta.stackexchange.com/a/58035/711182, it's not spam. In this case, what are the appropriate actions? Downvoting doesn't really stop the user from posting the same thing again and again (the first, already deleted, posts appeared several years ago). Explaining anything to the user is hopeless.

  • 5
    Is there something that prevents the correct handling of the posts? I mean, downvoting and deleting the posts can still work, right? What is left is the cross-posting of seemingly the same content across sites, right?
    – rene
    Sep 22, 2022 at 20:24
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    1) deleting the posts - with what justification? Sometimes, with a bit of a stretch, it can be on-topic. 2) Deleting doesn't prevent the user from posting again (on the same or on a different site), maybe with some delay. 3) Yes, what's left is a cross-posting, which is a noticeable part of an issue. 4) I'm basically looking for concrete actions I can take, such as a correct closure flag, and how to prevent this behavior from repeating.
    – Dmitry
    Sep 22, 2022 at 20:31
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    But reposting after posts have been deleted is behavior that is mod-flag worthy.
    – rene
    Sep 22, 2022 at 20:37
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    OK, so the algorithm is the following, correct? 1) Flag the post with "requires moderator attention", write that the post should be deleted because <not sure what goes here>, and reference this discussion. 2) If the post is deleted, and the user posts a similar thing again, flag the post as "requires moderator attention" with explaining the situation and a suggestion to suspend the user (otherwise, they'll just post again)?
    – Dmitry
    Sep 22, 2022 at 20:42
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    They should be deleted for any and all of the same reasons that any other post could be deleted. If you don't know enough about a particular community's expectations in that regard, either flag for a moderator with your own justification, or leave it for them to sort out on their own.
    – Nij
    Sep 22, 2022 at 23:02
  • @Dmitry in this case I could have raised a mod flag stating: I'm not enough of an SME to judge if this post is on topic but given similar posts got cross-posted [here](link to post) and [here](link to post) there might be more history that warrants action beyond closing and deleting. Can you investigate / discuss with the other sites mods and then decide on the best way forward. After that I use my own judgement on the content and vote (down. close, delete) accordingly. The latter is important in case the mod decides no action is needed while the community still feels the posts need to go.
    – rene
    Sep 23, 2022 at 5:48
  • Can you explain the history a bit more clearly? Because, from the evidence provided in the question, it seems like we're getting all worked up over a couple of posts. Of the 5 links you have given, only two have questions or answers from the same user. Maybe three if the deleted one is similar. Is this really a problem?
    – terdon
    Oct 2, 2022 at 11:01
  • @terdon Check the user's network history, it's basically all they ever post about.
    – F1Krazy
    Oct 2, 2022 at 11:16
  • @F1Krazy not sure what to look for. Yes, I saw several (three) posts on SO about the halting problem, but nothing obvious in the other accounts. I'm not saying Dmitri is wrong, I am just saying that the problem isn't particularly clear from the evidence presented.
    – terdon
    Oct 2, 2022 at 11:18
  • @terdon, basically, the user spams with the same idea across the network. They posted them multiple times on cs.stackexchange.com . After that (presumably after seeing that there is no effect), they started to post it across other sites (regardless of relevance), as I show in the post. I believe that it's not what we what to see, and my post is about the actions that should be taken to prevent it. (If you don't think it's bad behavior based on what I presented, I guess it's fine: we all can have different opinions, and it's not like "bad behavior" is defined rigorously)
    – Dmitry
    Oct 2, 2022 at 18:56
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    @terdon, I'm afraid you won't be able to see the full history: there are a number of posts that have been deleted and won't be visible to you (unless you happen to have 10K rep on the appropriate site). I think it's reasonable to ask for what information can be provided about the history, and I apologize that I can't help with that, but I've written an answer below about how I would recommend handling this particular situation.
    – D.W.
    Oct 3, 2022 at 21:57

2 Answers 2


General comments on cross-posting

Different sites have different policies on cross-posting. Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site? has some discussion.

I tend to follow Jeff's guideline "Just to be 100% clear, copy-pasting a question across sites with no changes is considered abusive behavior."—this is the most common scenario I encounter, and normally I see these when a user flags them with a custom flag for moderator attention, or in a comment where another user has identified the duplicate. I ordinarily just close the post with a custom reason and a link to one version of the question to keep, and leave a comment explaining the policy to the user. It's not a serious violation, just a mistake not knowing customs, and for most users does not recur after they're made aware.

This scenario is not a typical cross-post

This scenario seems a bit different, though. It's less that the user is reposting a single question; rather they seem like they want to engage in a discussion about a topic that interests them rather than ask a real question. Effectively, they're just self-promoting some (I assume crank) theory of theirs. It's not especially significant that they are doing this on multiple sites, and this would not be welcome behavior for a single post on any one site.

I think this is the sort of exception for which human exception handlers are built. Flag for moderator attention, include relevant context you have (though know that if this is a repeat occurrence on a particular site, the moderators there will probably be familiar), and downvote if you'd like.


I'm familiar with this specific situation. I think the best mechanisms to handle this specific situation are our site's existing quality-control mechanisms, including downvotes, close votes, and flagging for moderator attention. I think we should communicate our community's norms and expectations, and then enforce them.

It's not personal -- it's just that there are certain kinds of use that Stack Exchange is designed for and works well for, and other kinds of content that are not a good fit here, and we need to enforce quality control to protect the smooth functioning of our sites.

Some examples of community's norms and expectations include:

  • Each question must ask a single, well-posed question.

  • Every answer must directly answer the specific question that was asked. We're not a general discussion forum, so general discussion of the broader topic or thoughts inspired by the question don't belong in the answer box.

  • We're not here to support debates or as a way to promote one person's ideas. Instead, we're here only for a very limited purpose: Q&A that admits answers that can be objectively evaluated based on criteria in the question. And, we are trying to support our broader mission of building up a high-quality archive of knowledge that will be useful to others, and Q&A is the way we work towards that mission.

  • We expect that people won't change the question after receiving answers (at least not in a way that invalidates existing answers).

You can help by taking action to support community norms and expectations:

  • Vote to close any question that tries to ask more than one question, solicits discussion/opinion, or is too broad (e.g., asks for too much to expect in a single question on a Stack Exchange site; review of a lengthy proof).

  • Downvote any question or answer that you don't find useful or helpful to appear on the site.

  • Flag any answer that doesn't directly answer the question that was asked.

  • If you see comments getting out of hand (e.g., being used for extended discussion), flag for moderator attention.

  • If you see a question literally being cross-posted, flag for moderator attention and highlight that it is a violation of Stack Exchange policy. That said, in this particular case, I'm not sure how much of the problematic content is a literal cross-post (a lot of it might be posts on multiple sites that are closely related but not a cross-post?).

  • If you see a situation that is not healthy for the community but isn't adequately addressed by the above mechanisms, flag for moderator attention. That's what they are there for: moderators exist to handle exceptional situations.

In this case, I think the user believes they have found a serious error in accepted wisdom and are trying to draw attention to this perceived error, and they aren't getting the kind of response they were hoping for, so they are repeatedly posting on many sites. Many folks have tried to explain what we suspect they might be misunderstanding (e.g., I tried, Raphael tried, Dan Doel tried, Doc Brown tried, and many others have tried in comment threads). I think that's all that can be expected, and beyond that, the best we can do is enforce site standards.


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