I think formally, i would go with the answer of @Chad and @Rarity here.
But as usual, i would try to start from your perspective and re-emphasis the point you are trying to make.
If you look at sites like Signal Processing, Quantitative finance, Cryptography, Physics - involves formal science behinds their core subjects which make sites very crisp and there is hardly any place for subjective (i.e. personal opinion based) questions or answers. Even there, personal judgement plays a role in terms of knowing right answers from wrong -but in general there are correct answers or wrong answers based on scientific view alone and not someone's personal thinking.
Sites like Workplace are many others like Parenting, OnStartups, Personal Productivity and so on, where people share their experiences and judgement. These are not based on any formal sciences like the one shown above so naturally, there is relatively higher level of subjective opinion. But to make it a great site, there still needs to have deep and great learning from both the questions and answers.
However, to maximize the value of such sites look carefully the following:
1. Chatty questions will have no value. When some one asks - "Should i do this?" and all the "Mee TOO" answer starts yelling ..NOOOOOOOOO. this makes things noisy and useless.
[example: Is it acceptable to use pirated software on the job? - beyond first couple of answer everything is noise and nothing new to learn.]
2. Personal bias or rants will not serve any good answers
I will give you two simple examples of what is NOT truly fact (i.e. figures and reference based) questions - but their content still distinguish and creates and impact on the value in terms of its constructiveness.
In the first question: Is there an effective way of dealing with nepotism at work? the OP has stated the fact that The cardinal-nephew problem is quite common in Greece
and in the second question https://workplace.stackexchange.com/questions/986/is-there-racism-in-software-egnineering-field OP claimed I have noticed that there is huge salary difference between a white american engineer and lets say a foreigner such as asian or Indian.
To put things in perspective 'nepotism' and 'racism' are both social phenomena and they are visible with different societies in different intensity. As far as facts and figures are concerned, neither of the question really quote any government data or UN report to conclude that such social anomaly exists really and if so, how much. So both have derived their question based on their personal experience; in this sense, it is subjective but this subjectivity is acceptable. [In physics i wouldn't be able to say "in my experience, speed of light is much less than sound!" - this is plain wrong and nothing else make sense further.]
... but irrespective of data of the context, there is a great difference in the two questions. in the first question OP simply saying that at least i have seen nepotism many places - if you have been through it, can you tell me what to do with it? This is perfect to ask, and given that great many people do go through the similar problems in life it is good service to society that there is some good answer to this. It doesn't matter that everyone's experience doesn't identically match as long as it is not a rare case. On the other hand, the second question is (horribly) biased - "I guess Americans are just abusing Indians or Asians you also think so? - well in a typical case i might just say well - 'you are right, these guys are just f## bs - we gotto do something about it!' ... so from the the second conversation there is nothing to learn from. In fact it is sympathy exchange and not even a question-answer session.
same way, when people write either questions or answers with notions like "bosses are always bad" and so on, it is very likely that your post is hardly of value. Many folks have different world view some are strong some are mild, we all have some bias of somethings; but the point is, when your bias, offensiveness, rudeness hijack your thinking, it doesn't help anyone else really. Which is why subjective post still needs to be dealt with with very very carefully.
3. Facts and figures or experiences?
As the message says
We expect answers to generally involve facts, references, or specific
expertise;
Now as i indicated above, in sites which involves formal sciences, without actual numbers or equations nothing would make sense. But here, you need to understand what is expected.
There is a good question here: How should I properly approach my boss if I'm feeling underpaid?
This question, and all answers goes in depth as to what to judge for a 10% raise? And there are great many answers there that gives interesting insights. Please note, none of these are concluding the 10% number based on benchmark data or text book theory. They are based on experience. These are people who have their own valid judgement and more importantly answer reflects why it is that way. I can also go back and reply - "10% seems good, why you are complaining?" but that is such a terrible answer.
Also, if OP wouldn't have said 10% - all answers were off the tangent. So such information is critical in making questions and answers of any use. If that 10% would have been 1% it is a complete different situation.
... so need to have facts in Q&A doesn't have to mean some kind of benchmarked universal metrics but it needs to be sound. This can be based on expertise as well, and it can come from personal experience rather than formal source, but it needs to be reasonable and of something where meaningful insight can be derived.
4. Opinions - ok or not?
This is perhaps most difficult to explain. In general, SE format says no opinions. Period. This is actually simple for formal subject sites. But sounds confusing in soft sites like this. Frankly, (may be i am wrong), every question and answer i have read here are only and only opinions. See: Is it professional to cut out a middle-man in a contract chain? - all answers are only opinions in true sense. However, the point of the answer isn't really that i am saying yes or no. It is the reasoning that is useful and anyone can learn from this. Which is why-
Questions liKe "Should I make 5 page long resume?" makes much terrible question over Why is a one to two page résumé recommended? In case of former i would only yell back saying that is a mistake, but in the later i would learn why and there can be multiple view points to it.
...it is important for all answer givers here to understand that even if it is asked for opinion it makes sense that you focus on why. Opinions differ but it is insight in the answers which is relevant makes it useful and you can learn from it.
5. Emotional outburst needs to be taken care
Many kids come home crying, "why did john hit me with his bat? How can he do that" This of course is a question, but it is much more of emotional outburst and a whole mix of questions in it. No mamma would have really answered such question well actually, and so is true for people here.
[See: Getting fired on the second day, how do I cope with it? ] this question was only an out burst.
... yet, it is an issue that should raise questions, but unless you cool down and talk fresh it becomes difficult to really answer in a meaningful way if at all it will be answerable. Most answer in case of above, were consoling and rather trying to answer "what i would do next time".
But yes, my opinion differs from others here only one respect that the fact that there is emotional content, the situation must be real. So there is a genuine problem to be solved there or something to learn from that experience. We shouldn't just slap the kid (by closing) who is already hurt from some place. We must try to get back to make OP to clean things up - may be re-write the question and help him/her crystallize the thinking to make it look good. I know for mods, it is such a painful job, but i think once users gets established, you don't have to do this always. Don't keep the tearful question in its state forever but at least be patient to improve upon it.
6. Does it have to be (my own) real problem?
Let's test the theory! Let me ask you "How was Hitlar, who was so arrogant, must have reacted when his people would have frowned for lack of raise?" I don't know if there are historians here, but even if they are, the answer to this question wont help me about what should i do during my appraisal (even if my boss is considered a hitler). The point is, hypothetical questions, even if not bad (not off topic nor a rant) are completely useless because they are so flawed because artificially created; and i would doubt any answer would make any sense if at all you can answer it.
people should understand that notion of "someone else will benefit" is wrong. as it is there are several factors that makes this site very subjective. If we ask hypothetical question (even if it doesn't start with hitler), it doesn't help because it will generate poor answers.
Is “not constructive” really applicable at workplace.SE?
Yes of course. And in the description of above, i don't think any SE guidelines are contradicted. It is just that meaning of words - subjective or opinion needs to be understood carefully.