I've read through all of this discussion, and the one thing that keeps popping out at me is the disconnect between both sides on who has the burden of proof.

Self-evidence

The crux of the argument in support of these types of answers, as I understand it, is that they aren't providing anything that necessitates detailed evidence, and such a requirement would be onerous on otherwise self-evident (or commonly-held) ideas.

Something that's self-evident is, by definition, something any reasonable person would know. By providing answers that are self-evident, you don't provide any expert value.

Take the classic example of someone coming to the IT guy for help with a computer issue they're having, and the IT guy responding, "Did you plug it in?" It's self-evident that a computer must be plugged in for it to work, but the exchanges speaks to anyone who's had to deal with really trivial computer questions; it's functionally equivalent to saying "You're wasting my time by asking me this question." It's been lampooned in many a comedy sketch because it's exactly the type of response nobody wants to receive when they're coming to someone for help.

Massively up-voted answers like the ones discussed here are our moral equivalent of "did you plug it in?" Someone asks a seemingly trivial question, someone else leaves the obvious response, and it gets massively up-voted not because the answer actually provided value or great insights, but because it said what we're all thinking.

That is decidedly not what Stack Exchange is about. If you don't think a question is worth answering with a thoughtful, well-reasoned response, there are several options available:

• Leave a comment explaining why the question is trivial and basic things the person can do
• Down-vote the question as showing no research or effort
• Vote to close the question as not constructive, too localized, or not a real question depending on the circumstances

But beyond that, the main premise behind Stack Exchange is that there are experts who are willing to help others who might not know as much as they do. It's important, crucial even, that self-evidence is just taken off the table entirely. The answer is not self-evident: if it was, it wouldn't have been asked.

Preferences vs. belief

Beyond the question of self-evidence is the issue of what constitutes subjectivity, and answers can be roughly categorized into two types:

• Personal preferences
• Warranted beliefs

A personal preference is something you personally like or favor for whatever reason: I like mint chocolate chip ice cream. I enjoy sleeping in late. I want a slice of pizza for lunch today. These are unassailable: provided I'm not lying to you, you can't prove I don't like mint chocolate chip ice cream, no matter how hard you try. I said it, it's true.

A personal preference is the appropriate answer to a question asking for a poll: "What is your favorite ice cream flavor?", "What's your favorite book?", "Which programming language do you like the most?" Those questions, however, are straight up prohibited here and across the network. Personal preferences have no place in an answer, and are the smell of a bad question.

A warranted belief, on the other hand, is something you personally believe based on something you personally know to be true. That is, "I know X, and I know it because of Y."

This, and only this, is what subjectivity is all about on the Stack Exchange network, and it's the heart of the "back it up" mantra. We want—no, crave—answers that provide a belief of yours that you hold because of some special, personal insight.

But it's not enough to just provide the belief: how do I know what you're saying is true or credible (remember, self-evidence is off the table)? Tell me more about why you believe that and I'll decide for myself whether what you believe is truly warranted from what you know, or if there's some other insight to be gleaned.

Summary

In short, the person who has the burden of proof is always, always the answerer. If you can't support or are unwilling to support your claim with information about why you believe the claim to be true, it's not worth leaving the answer.

It wastes everyone's time: the question asker who doesn't get a useful answer, visitors who have to read through the answers, and yours when you have to justify it to people who question the claims made in your answer. To respect people's time, and make the internet a better place for everyone, tell us something we don't know and explain what it's all about.

Answers are like show-and-tell: we're all dying to hear the story behind why you believe PHP is the devil's work, or how you came up with the idea to use recursion to save little Timmy from the well. Don't hold out on us.