We have always had canonical questions/answers, it’s just that until Danu’s post here in the Meta we didn’t call them canonical. A canonical question/answer is one where the question is so apposite and the answer so clearly explained it ends up being cited many times. Sorting the questions by votes will quickly reveal many such questions. My own favourites include (to list just a few):
Though of course everyone will have their own favourites.
Now, the Physics SE isn’t a blog and shouldn’t be treated like one. If we all started writing what amounted to blog posts just because there was some subject that we found fascinating that would quickly alienate the site members. Setting out to deliberately write a canonical Q/A (as opposed to achieving it as a side effect, like the three examples above) is something that shouldn’t be undertaken lightly.
While I want to keep things general and avoid specific issues let’s take the three Q/As of mine that John mentions as an example.
As the most prolific poster of answers on this site (note that I’m claiming no special merit here, unless you regard fecundity as a virtue :-) I have seen lots and lots of questions and answers - I’ve probably at least glanced at every question on the site for the last five years. As a result I get a feel for when the same topic is being questioned again and again, and the question What is time in its various forms has been asked countless times. When this finally annoyed me once too often I posted on the Meta asking:
Canonical question about the flow of time
and got the general impression that a deliberate attempt at a canonical Q/A would be well received. Even then it took me a month to decide how best to write one. So this was not a spur of the moment impulse because I was bored. It was a considered decision based on consultation. In the end I wrote three questions, but they’re all one Q/A really - I just split them into three to make them more digestible.
Whether or not my three recent Q/As are a long term benefit to this community remains to be seen. I’ve already used them several times as duplicates, or I’ve posted them in comments as a related question, but I haven’t attempted to analyse how many times others have linked them. They have ended up with a middling number of upvotes, but as John says the number of upvotes is a poor guide to quality, especially when a question makes the Hot Questions list as at least one of mine did.
However the question of canonical Q/As is broader than just the three questions mentioned in John’s question. I have linked my three favourite Q/As mentioned above many, many times, and the site would be a considerably poorer place without them. But of course those questions weren’t deliberately posted to be canonical, they just happened to hit the target, and I think the crux of John’s question is:
Should site members deliberately post questions and answers intended to be canonical?
Perhaps surprisingly my answer to this is that no they should not. Just because a subject seems interesting to you is no guarantee that it will be interesting to anyone else, and no guarantee that an attempted canonical Q/A on the subject will be useful. You should at the very least discuss it in the Meta before posting, and perhaps bring it up at the fortnightly physics chats before setting pen to paper.
A last point, and again this is a general point although I’ll address the specific issue of the Q/As mentioned by John. Posting a canonical question and answer does not mean no-one else can answer the question. Indeed, there are frequently many different perspectives on a complicated issue and ideally a canonical question will attract answers from several site members who want to post different perspectives. Indeed this is what has happened with all three of the questions that John mentions. Naturally I think my own answers are the best :-), and they have attracted the most upvotes, but anyone add their own answer if they think they can do a better job.