Can cross-posts actually be valuable to two communities, with the exception of being worded identically?

Question

I'm posing this question in order to confirm the correctness of my answer to "Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site?" which is answered with:

NO

Ask the question on the site you think is most applicable. If, like in this case, it does not get any answer, ask a moderator to migrate the question, or alternatively, delete it and re-ask it.

I didn't understand this answer when I first read it. I still don't, it leaves me wanting to know "Why?". I believe the answer is "yes and no" and I'd like to discuss that reasoning here.

My question is, can cross-posts indeed be valuable to two communities, with the exception of being worded identically?

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Here's an excerpt from my answer:

I've discussed the no-cross-post debates over the months and I never could understand what was wrong with posting an identical question on two sites when it was perfect for both sites as-is. A question that I thought was fair to cross-post was:

• Valuable to both communities
• Worded perfectly for both communities without any change or "tailoring" needed
• with the intent of getting two diverse kinds of answers on the question
• not just to get an answer faster

This belief was confirmed by answers like this:

In the edge case where the question is appropriate on more than one site, leave it on both sites and let the users of each community benefit from the information.

And the discussion point:

Here's the real underlying problem: The SE Network was not designed for duplicate questions across sites.

Because the SE Network is designed to work as a unified tool, combining questions from all sites, identical posts are oddballs.

...

To anyone who says duplicate questions a bad in all cases, that's simply wrong! When questions are cross-posted with the right reasons in mind, in the right situations, there's nothing wrong with them, except the issue that I mentioned (the SE network's unified functionality).

Answer 1

^{_{We're here again?}}

A good question is very unlikely to be identical on multiple sites

I've discussed the no-cross-post debates over the months and I never could understand what was wrong with posting an identical question on two sites when it was perfect for both sites as-is.

It is pure hubris to contend that a given question is perfect for multiple sites. Each site has its own set of expectations of what a good question is. Each site has its own focus to what types of topics it covers. When the identical wording is posted on multiple sites, it is quite likely to be too broad or unclear, assuming that it is on topic on each site.

Optimize for the single answer

One should consider precisely the single answer that one wants to the question and post it on the appropriate site. This is the criteria. Not if each community will find it interesting or not (I look on reddit for interesting things), not if it is "perfectly" worded.

I follow a number of tags on different stack exchanges through email updates and filtered questions. Let me decide what interesting.

diverse answers can be a problem

Getting a diverse set of answers points to another likely problem with the question - that there is no one answer. Getting a range of answers means that there is less likely an authoritative answer on the subject (The halting problem - or - the fallacy of “real questions have answers” touches on this).

On wasting time

answering

You have a problem. You are looking for how to solve it. You ask on Foo.SE and Bar.SE about how to solve it. Someone on Foo has an answer that solves it - great. But now people laboring over the problem on Bar.SE are wasting their time because the problem is already solved.

Posting to multiple sites wastes the time of the people answering it on the other site when there is already an answer to the problem on another site.

on improving the question

It is unlikely that this question is a 'perfect' one. Please accept that. Given this, it is then up to the community to tease out the details that are pertinent to that community and modify it so that it does present a question focused on their specialty. When this is done on multiple sites, it wastes the time of multiple communities to tease out the pertinent details.

on migrating and mods

One approach to this is for the question to be migrated to the other site where it is gathering the most attention or would likely get the best answers. I will point out that this is an area of debate - that one should try to cultivate each Stack Exchange independently (if there is a question on one SE, one should try to make it a good question for that SE rather than sending it to another one).

However, migration takes time. If you have gained answers on both sites and it is migrated (something that occasionally happens with cross postings between Programmers.SE and Stack Overflow), it requires either a mod to move it (SO to P.SE) or 5 close votes (P.SE to SO), and then 5 more close votes (dup) and then a merge (mod handles a flag). This wastes a lot of time that could have been better spent elsewhere.

on people finding the answer

A key part of Stack Exchange's value proposition is that it is the place to go to for the answer. One spot. The 'one' is important. Stack Exchange exists as an alternative to the forums for trying to get answers - having to search through pages and pages and sites upon sites trying to find the answer.

By scattering answers across the network to a single question one wastes the time of the people trying to find the answer and this in turn reduces the value of Stack Exchange's value proposition and diminishes the brand.

In short...

Don't post the same question on multiple sites. It wastes the time of people answering the question, of people trying to gather the answers into one place, of the people trying to find the question... and is unlikely written to be a good question on each site in the first place.

Answer 2

I wrote a pretty good answer on Arqade as to why cross posting questions tends to be problematic. The core argument is that even if the question is the exact same, the answers won't be, and will make assumptions on core competencies and approach taken. I particularly like the last paragraph:

The reason cross-posting is frowned upon is because it's the hallmark of a vague question. If it's broad enough to be equally applicable to multiple SE sites, you haven't refined the question enough. More thought needs to be invested to see which group would be best able to answer your question. You need to decide which site you think has the best chance of answering the question. If you don't manage to get an answer, feel free to delete and ask on another. That way, there's no duplication of effort, no bickering, and if you get an answer on another site, it will be applicable to those that view it.

So, not only do you get different answers and waste people's time, but the question itself is probably too vague. There may be some edge cases where a question would be valid on multiple sites, but so far, I have yet to see any of those types of questions. Rather, they are vaguely thought out questions where the root problem hasn't actually been properly defined yet.

Spend more time digging down to the actual problem, and that usually narrows the site to ask it on to a single one.

Answer 3

If you post a question on site A and site B and you get two answers that cover the same ground, which is likely except in extreme cases where two disciplines completely differ on their approach to a problem, you've wasted the time of at least one of those people who have answered.

Also, a high percentage of people that follow cross-disciplinary tags (e.g, biochemistry on Chem and Bio) tend to be active on both sites anyway.

While cross-posting is not against any formal rule on SE, people have tended to observe this policy as a matter of courtesy on the internet for decades.