Are non-verbal answers (and questions soliciting them) acceptable?

Question

Recently, there has been an answer to a question asking for 'A word, gesture or expression for a confident “shrug” ' which invites and was presented with a captioned photograph illustrating this. The caption was not, in my opinion, an idiomatic expression. Are non-verbal answers acceptable? Does the 'gesture' tag need a caveat?

Answer 1

nothing to hide

If the question is really seeking, fundamentally, body language (and not terms for body language), as in, the only way to answer is with a photo, then no, off-topic.

In this case, seems like the OP is an author looking for ways to phrase a certain idea for his readers, i.e. he's looking for language. Now, if this were simply "ghostwriting" (what's the best/clearest/interesting, colorful way to phrase this idea, etc), my stance is that is also off-topic (and I think I'd get general support for this from other regulars; maybe it'd be on-topic at Writers.se, I don't know, but it should not be on-topic here).

But the way this is phrased, it's equivalent to the question offering a picture and saying "what is the English term for this?", which is on-topic in my view.

everything to gain

But given the question I just linked in support of that view -- which I also answered, you'll note -- is closed, on what strength do I make that assertion?

On long-standing consensus on EL&U on what makes a good question. In short, they (a) well-specified and admitting of objective answers, and (b) providing those answers requires expertise in English.

1. Asking "what does the word W mean" is off-topic, because finding the answer to that question is trivial on one's own, i.e. checking a dictionary, which are tools dedicated to that specific task.
2. But asking "What is a word which has the meaning M" is on-topic, because this is a non-trivial task which requires expertise and a strong command of English as a language, which is the core competency EL&U offers to the world.
   1. For those with a CS background, (1) above corresponds to a O(1) operation (handwaving a bit about the hashing function); (2) here is at the very least O(n) (n being the 0.5-1 million words in the English language) if the phrasing you're looking to map happens to correspond to the way a dictionary has glossed it. But since English is generative, the odds of that are low indeed; I expect that this task is actually NP-hard.
3. Given this state of affairs, the site historically has been very receptive to such questions:single-word-requests is our top tag and it also has popular cousins (e.g. phrase-requests, idiom-requests).
   1. It would be disingenuous to say that everyone likes these types of questions or that there haven't been appeals on Meta to limit or eliminate them (as "guessing games"); nonetheless a broader consensus has developed and maintained keeping them.
   2. Even with that caveat in mind, there's another class of questions which doesn't seem to cause much, if any, contention on Meta; in fact, this class seems to have appeal even in our most jaded and/or conservative constituency: "In French, we say avoir le cul bordé de nouilles; what's the English equivalent?", aka translation questions.
   3. I'd argue "what is the English word for this gesture/face/body language" is much more analogous to the latter than the former, because we know, in advance, the specific meaning we are seeking (a foreign phrase or a gesture has a known meaning which allows for a canonical answer), and so doesn't fall afoul of the "guessing game" trap (where the question invites answers which are more like design than engineering; the querent has some vague impression of what he wants, but will only know it's right when he sees it; it cannot be perfectly specified in advance).

exceptions prove the rule

Now, having said that, while the argument above makes the case that there's no reason to foreclose such questions as a class, it is still possible that a particular instance may be off-topic.

For example, if someone posted a picture of a person smiling, and asked "what's the English word for this facial expression?", we should close it as off-topic under our standard rubric of "questions which would not occur to a native speaker; or which a native speaker would immediately and intuitively know the answer to" (aka too basic).

tl;dr

We should treat such questions as generally equivalent to translation questions at best (some of our favorites) and single-word-requests (mixed views) at worst, aka on-topic by default.

But, just like always, questions can be off-topic for more than one reason, and that a question passes muster under some rule doesn't mean it doesn't fall afoul of another, so each should be considered on its individual merits.

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<sub>PS: in re the specific Q/A you cite as motivating this more general question:

I agree with your core critique on that answer. That is, I don't see the issue here as that the Q is off-topic (it's not), nor that the answer included a photo (that's fine; usually doing so adds color to otherwise flat text), but the phrase "nothing-to-hide" gesture doesn't carry any particular currency, and that some person out there once titled a particular photo with that phrase doesn't count as "authoritative support" in my view. The usual response to answers we disagree with on the platform is to downvote them, and that's usually the extent of our reach.

Which is to say, I don't think answers to this meta question apply concretely to that main-site question or the answer you've linked to. If you don't like the answer, that's fine; downvote it, if you like, and move on.</sub>