When are questions on culture-dependent non-verbal communication on-topic?

Question

We have at least two questions dealing with non-verbal communication that may be specific to German-speaking countries or regions:

• Do Germans count on fingers starting from the thumb? – No close vote or flag was ever cast on this question. It has 26 upvotes, more than four thousand views and was a hot network question.

• Why do German students knock on the desk? – This question received four direct close votes and one from review, “because it is about culture, but (explicitly) not about language”. Nobody voted to leave it open or reopen it. It has +3/−1 votes.

^{The above information is as of writing this post and subject to change.}

As these questions were received in quite a different manner, I am asking:

• Under what conditions, if any, are questions about non-verbal communication on-topic?
• In what respect, if any, do the above questions differ in respect to their on-topicness?
• Are we happy with the different treatment of the above questions?

Clarification: To keep the discussion straightforward, I suggest to exclude sign language from this. (Not that I am saying that it should necessarily be treated differently.)

Answer 1

This basically is the other half of "are germanic languages other than german on topic?"

I posit:

Questions about non-verbal communication should always be on-topic, as long as it's sufficiently clear that some kind of culture speciality of a German speaking country is involved.

Language should thus not be limited to Written or Spoken language, but should positively include symbolic languages like Sign Language in a sense encompassing Gebärdensprache, "Street sign symbolism", and whatnot; as well as gestures, facial expressions, etc.

Given the above definition:

If a distinction between another language culture space and a feat of a German-speaking cultural space can be made, a question should be on-topic, even if the language involved is neither written nor spoken.

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That said, the knocking question should stay open if it is or becomes clear that this is indeed some special signalling behaviour that can be witnessed in German-speaking countries, but not in ((m)any) others.

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Example, why a symbol language (road signs) should qualify as an endemic, non-verbal language of the german cultural space:

German road signs convey universal meaning through their own, german-culture-space-specific vocabulary (the symbols and colors), possess their own (Chomsky) grammar based on local laws (a /!\ may be used on its own, but it can be combined with certain detail sign additions, for which not all parts of the vocabulary qualify) and are thus specific to Germany or other German speaking countries, with overlaps in related sign languages (road signs from other language spaces) like in verbal languages. The Stop sign, for example, is pretty much the "Mama" word of road sign languages

Answer 2

I think the first close vote on the "knocking on desk" question was cast by me.

It is a very common phenomenon that people find it much easier to follow someone's suggestion than to be the first to point something out.

The reason I did not cast a close vote on the "counting" question was that I simply had not noticed it.

In my opinion, if the channel was about everything specific to Germany, it should not be called "German language".

For me, neither of the two questions has to do with language. Nor do I think the behaviour discussed in each of them is something you only find in German speaking countries, but I may be wrong there.