TL;DR
Current consensus is to delete short answers.
My personal vote would be to allow some (not all) short answers, only if they are good answers.
The moderators should do what the community decides
Moderators shouldn't delete answers which their community would want them to keep. I assume we can take it for granted that no-one wants spam, nor anything unintelligible nor utterly off-topic, but apart from that we should look for some community consensus (which is why you opened this meta-topic).
For example see how its author worded this comment:
That notice is pretty much designed for Skeptics, which does have such a policy because of the inherent nature of that site. Skeptics specifically want citations for claims, and their community allows their mods to delete uncited answers.
That says "their community allows their mods" because that community discussed and voted on that policy on their meta site (for example, here and here and here and not to mention all of these).
Maybe moderators should wait until a user flags an answer
FWIW in the past if I disliked an answer, I decided to delay deleting it (i.e. not delete it now) and instead wait to see whether someone else flags it. Because if someone else flags then at least I know there are two people (i.e. me and someone else) who dislike it.
The answer you're talking about was flagged, but it was flagged by the 'Community' bot for being short, not flagged by a real user who could read it.
Just because it's short doesn't mean it's good
We should try to reserve the right to delete some short answers: not every short reply is in any way a useful answer.
Current or previous community consensus
This topic has been discussed before: Should we allow/encourage short answers?
It seems to me that:
- Several people answered that we should allow them
- Two people (Hrafn and you) answered that we shouldn't, and those answers got by far the most votes
So I think that the current or previous consensus was that short (mysterious) answers are never allowed.
Just because it's short doesn't mean it's bad
yuttadhammo posted links to where this has been discussed on many other sites, and wrote
I've taken a look around SE, and it seems the consensus is actually to allow very short questions, as long as they do actually answer the question. Here's some of the reasoning.
Just because it's short doesn't mean it's mysterious
I might agree that a mysterious answer isn't helpful.
But this answer wasn't very mysterious, it was on-topic, it was about the same length as the question, maybe just long enough to express their considered opinion without starting to write a thesis on what else you could to be doing instead of buying a statue (which would be an answer to a different question).
What about voting?
Theoretically, instead of deleting an answer, people can downvote bad answers.
If the users on this site would upvote (good answers) more and downvote (bad answers) more, that would help in many ways.
This help topic suggests that answers can be deleted if they have a score of -1
Moderators can delete any answer, and trusted community members can vote to delete answers scoring -1 or lower (3 votes will result in deletion).
On a mature site people would vote; on a beta site there may not be enough people actively voting yet, and for that reason moderators intervene with their unilateral/binding actions.
Why are answers ever deleted?
This same help topic says,
Answers that do not fundamentally answer the question may be
removed. This includes answers that are:
- commentary on the question or other answers
- asking another, different question
- “thanks!” or “me too!” responses
- exact duplicates of other answers
- barely more than a link to an external site
- not even a partial answer to the actual question
Note that "too short" is NOT one of the reasons listed above.
What about posting a comment?
I think we should use comments, to ask for any specific clarification or to suggest some specific improvements. If you don't delete an answer then someone can post a comment, and/or upvote or downvote.
A comment that just says "this answer is too short" isn't necessarily constructive (everyone can already see it's short, what's less obvious is what if anything ought to be added to make it longer).
What about turning the answer into a comment?
One of the moderator tools lets you convert an answer to a comment. If it's short then physically it's not too long to be comment. If it doesn't answer the question (if it's "advice instead of an answer") then maybe it shouldn't be posted as an answer (regardless of its length) but could perhaps be posted as a comment under the question.