A Response To Aaron Bertrand
Not long after posting this question my voice was removed from this discussion. I feel this unfairly robbed me of an opportunity to engage with a discussion that I instigated and feel I have a right to be a part of. I am posting this answer in lieu of that opportunity.
I posted the question in good faith and with a genuine curiosity as to how Stack Exchange is changing and could be changed. I am once again put in the position where I have gently tried to instigate a discussion and suddenly I am under fire. Through this interface I have been told that my question is a duplicate, not in good standing within the community but simulataneous elicits a response over a few hours and debate amongst staff and moderators. Which is it?
I have mixed quotes of now-deleted comments as some are not addressed in the answer by @AaronBertrand.
It has never been trialled, and the FAQ provides enough reasons why
As my question already states, the FAQ speculates on reasons why it would fail, with no data. Also, I was also interested any mandatory comments for votes system, not just down-votes
Has a mandatory comment system for any kind of vote (up, down or otherwise) ever been trialled on a Stack Exchange site?
The assumption was that down-votes were the focus. That is not what my question asked.
The main question:, paraphrased:
Has Stack Overflow ever experimented with a system where down-votes required an explanation?
That is incorrect and I reject this reading of my question. You infer I am only interested in down-votes. Do not misrepresent the question.
To be fair, we'd also need to force an explanation for up-votes.
Would we? I think they are mutually exclusive. Up votes count for 10+ rep and down for -2 rep so there is already a disparity there. As the comment by @ColleenV points out below, any mandatory comment for up-votes has potential benefits as well as pitfalls.
The reality is like elections in the real world, I am free to vote (up OR down) for whatever reason I feel like and, to be frank, none of your business.
Conflating voting in a election with voting on Stack Exchange is a massive misrepresentation as to purpose of voting on SE. In an election we vote for politicians who make a claim to best represent outr interests. On SE we vote on value of a questions on those who have come to us asking for help and values of the answer from those providing help. How are those the same?
Side note: Other democratic voting systems outside the two-party up/down yes/no exist.
If you force me to pick a reason, I am sometimes going to pick something arbitrary and not real,
Arbitrary voting is already happening, it just can't be easily measured. Surely the idea of moving towards some level of accountability is positive. "Our users approach the system with such bad faith we're worried they will double down." is not a glowing report of the SE community.
so what value does such a system have when you can't necessarily rely on it?
One already cannot rely on the system. This sounds less like "if it aint broke, don't fix" and more of a "it's already broken, don't break it further", which is not a valid reason for inaction.
I am suddenly being forced to talk about this in terms of action and inaction. I just wanted to know if anything had been done in the past, this was not intended as call to arms and I resent the question being portrayed as such.
How would you even begin to measure "success" of such a trial.
and also
Most importantly, I don't know how you would possibly begin to evaluate whether such a trial was successful, or exactly how it directly influenced changes in user behavior. You'd see changes, for sure, but it would be hard to analyze net positive.
I said nothing about success. I was asking about effects on behaviour, good, bad and agnostic. I was asking wether data of that kind had even been collected and analyzed not a measurement of success.
but it would be hard to analyze net positive.
What about net negative?
It's funny how nobody ever comes here requesting that users should have to associate a qualiatative reason for an up-vote or an accept.
It's funny how users seem to read the question they want to see rather than the one I have written
Why is it that nobody comes to meta asking us to force an explanation for up-votes?
Has a mandatory comment system for any kind of vote (up, down or otherwise) ever been trialled on a Stack Exchange site?
again, from my questions:
up, down or otherwise

@ShadoWizardChasingStars But I'm not offering up any ideas that haven't been discussed ad nauseum here on every other related discussion over the years. Just doing the OP a solid because they haven't found those yet.
I have read the disussions of other posts, I have seen the answers and justifications included within. I was looking to see if anything had ever been tried to back up those justifications. That is all.
You have engaged in a discussion at a point you knew full well my account was suspended and that I would be unable to respond. You have misrepresented my question and patronised me.
I can assure you, you have not done me "a solid"

Another thought that occurred to me is that such a system could have a different negative impact (in addition to not really being able to rely on what the chose / wrote and often the often-discussed potential retaliation factor): endless debating in the comments, e.g. "I down-voted because {x}" "Well it's not {x} because {blah}" This is not what comments are for but it is absolutely how the will be abused and how the whole post will get derailed.
Lovely, that finally sounds like the start of an honest debate. Again, I was not asking what might happen, but what did happen in a trial if it took place.
I totally agree with you. A naïve implementation would create a lot of work and extra noise, but that doesn't mean the idea is bad, just that particular excecution of the idea.
Did anyone discuss some alternatives?
- What about a vote lottery, every user has to explain an up/down/ vote every
N
times, with some randomness thrown in?
- Rather than a comment, a down-vote goes into a private message box without reply? It's not there to start a debate, it can still be flagged for breaking code of conduct. The comment just adds some flavour to the vote.
- What about every Nth vote (up OR down) requires justification. You see a question already is ±5, you have to give a reason why you want to pile on.
- What if it only applies to new users. Would new users not be on-boarded quicker with some guidance from a real human being?
- Rather than a free text box, what about the same set of options as a question flag? This would go towards answering the redundancy of extra comments. "N users thought your question required clarity (link to article), but X users liked how you listed what you had tried"
- A combination of the above?
I was not trying to advocate for the feature, I was curious what had been found or if any of these kinds of ideas had been thrown around.
I'd be much more in favor of a way to voluntarily post an anonymous comment that is still tied back to me for auditing and moderation purposes, just not visible to readers. That won't eliminate abuse but should keep it to a minimum. This has been discussed before as well.
Even better, that in and of itself is acceptable answer to the question, in particular the part:
SE employees: if the idea has been floated, but tabled what was the thinking behind that?
Nobody owes you an explanation
Partially disagree. I think there should be more accountability on SE for sure. How that happens I am not sure, it feels like mandatory comment might be a step, but only with careful implementation and with some data to back it.
If people wanted to associate themselves with a qualitative comment to go along with their down-vote, they'd already be doing it, and it wouldn't need to be mandatory.
Is in opposition to your view. to this from the community wiki article:
Stack Exchange, Inc. is actually doing a hell of a lot to make the place feel more friendly.
You could just as well say, "if our users wanted to be held accountable, they would do it". Again, you seem to be saying the system is already broken and not worth fixing. Accountability doesn't typically work if it is voluntary.
As discussed many times, forcing an entry will almost certainly lead to at least some non-trivial percentage of inaccurate and less useful explanations.
Paraphrased: "No information is better than bad information". I think we are on shaky ground without data as to wether this would actually transpire.
Implementation would be complex, because if I'm the first person to vote a particular way on a post, I'm forced to provide an explanation. If I'm not the first, do I need to provide my own unique explanation? What if it's identical to a previous voter's explanation? Either implementation becomes harder to provide exceptions or a slightly different workflow, or it leads to a boatload of extra, redundant noise.
"Either implementation" is not the full set of potential implementations of the idea.
Selfishly, there are much more important things I would prefer our developers spend time and effort on.
I feel this is the most honest part of your answer. My questions is not a call for the feature, and it definitely it is not a call for it to implemented immediately. There are always more important things to do, that is a given. Just because something is not immediately pressing, doesn't mean it is never worth trying, does it?
Additional Notes
What I did not define in my question was the idea behind the requests for a mandatory comment for votes system the many executions of the idea, because I didn't feel it would be required. On reflection that may have been a mistake.
The idea I have inferred behind requests for mandatory comment is "Make onboarding users to an ideal Stack Exchange workflow more graceful and dignified". If that is not the idea that others have inferred, then we are sadly talking at cross purposes.
A suggested execution of that idea is a "mandatory comment for votes system", more broadly a "mandatory qualatative engagement for votes system".
My question was basically if a "mandatory qualatative engagement for votes system" had been trialled at any point on SE, which I feel is not particularly controversial. Why this question has drawn such ire I (ironically) fail to understand.
I think part of the friction of a "mandatory comment" proposal is down to multifunctionality of comments themselves. They act as a place to
- give feedback about a question
- illicit further discussion
- add more context to answers that don't deserve their own answer.
Grafting something extra on top of that system will definitely have unintended impact on some of these modes of use.