please define which languages are ontopic here and which are not, preferably in a way that can be concisely and objectively defined so that a reader of the FAQ can quickly decide if their given question is ontopic.
For further explanations and justifications see my previous answer. I don't want to add the following to it after some people have supported it, as some might consider it a substantial extension.
In real life there is usually a grey zone between social prohibitions ("you just don't do that!") and legal prohibitions. This is by design. Whenever that grey zone is too small or completely absent (e.g. copyright), it leads to conflict. The purpose of laws is to prevent frequent conflict between citizens through the deterrent effect of occasional conflict between citizen and state. This goal cannot be reached if too many citizens consider a law unjust because it regulates things beyond their own personal judgement. Social prohibitions don't closely mirror legal prohibitions - even laws always have edge cases that need interpretation, and this is even more true for social prohibitions, which are just statistical phenomena.
There is also another grey zone between legal prohibitions and their enforcement. If I technically break the law it's still quite possible that police and prosecutors have no interest in pursuing the matter because they consider it a trifle and a waste of time.
In our case, social prohibitions correspond to how questions that are actually asked on German Language SE are restricted. This restriction is in part a consequence of how people interpret the site's name. But it also has a dynamic component: If I google for a specific question and I find a very similar one that was answered on Stack Exchange, I am likely to ask my question on the same site provided that it isn't obviously out of scope. Legal prohibitions correspond to the scope rule we are looking for.
Currently, most questions on the Yiddish language that are unrelated to Judaism are de facto at least in the grey zone. In fact, most that have been asked are obviously on-topic in the strictest sense because they are sufficiently related to German itself. Since these questions do not, and are not likely to, present any problems for the site, it is expedient to find a scope definition that includes them. (It would also be possible to use a scope definition that excludes them but not to police it strictly. However, just like that didn't work for Wikipedia in the long run, Stack Exchange now seems to have the same problem with lack of common sense among site functionaries when it comes to application of rules. (Maybe there is a natural law of the internet that the self-governance of social communities automatically has problems similar to those described by high-functioning autists, e.g. in The Unwritten Rules of Social Relationships: Decoding Social Mysteries Through the Unique Perspectives of Autism. The strong American influence might also be a factor, since schools and the police force seem to have very similar issues in some places in the US.)
I think there haven't been many questions on North or East Frisian, but I think we can all agree that it would be very unfortunate if the scope definition included Bavarian and Swiss German but not these. (North and East Frisian varieties are often considered German dialects, and West Frisian varieties are often considered Dutch dialects. Functionally that's what they are. But genetically they are really all dialects of Frisian, a language that is placed somewhere between German/Dutch and English. It's the closest relative of English if you consider Scots a dialect as some people do.)
The smallest relatively standard linguistic category that includes German with all its dialects including North Frisian and East Frisian is called continental West Germanic. It can roughly be split into two groups: (1) Frisian (2) Dutch and German. Two offspring languages (Afrikaans and Yiddish) have been influenced by non-Indoeuropean languages but are still close enough to their ancestral languages (hardly more different than a typical pure dialect) to be included in the second group. Source.
Continental West Germanic is not an appropriate scope for pragmatic reasons, and cutting off Frisian would only make things worse. This should become clear when looking at the speaker statistics (numbers from the Wikipedia articles):
- German has about 100 million native and L2 speakers and up to another 100 million foreign language speakers. (For the other languages, the numbers of foreign language speakers are insignificant.)
- Dutch: about 30 million speakers.
- Afrikaans: about 17 million speakers.
- Swiss German: about 4.5 million speakers.
- Yiddish: about 1.5 million speakers (rough estimate).
- Frisian: about 0.5 million speakers.
- Luxembourgish: less than 0.5 million speakers.
People asking about Dutch would not be well served at German Language SE. For a major European national language one can expect better than getting opinions from a bunch of speakers of a neighbour language. While I like the idea of Dutch speakers and German speakers interacting at a single site, I am afraid both languages are too 'big', so that the friction would outweigh the synergies. It would make a lot more sense to group Dutch and Afrikaans together. By also putting the culture of Dutch-speaking countries in scope, as well as the Dutch aspects of Afrikaans-speaking countries, I think one could get critical mass for a separate site.
I might see things differently if we had a status quo of lots of Dutch-related questions being asked and answered at German Language SE. But there isn't even a tag for them, so it appears that basically it just doesn't happen.
Even in academia it is not unheard-of to exclude a subclass from a category for pragmatic reasons. E.g., instead of a clean definition of the clade dinosaur, biology uses one that specifically excludes the subclade bird. So it's perfectly fine to define our scope as follows:
Continental West Germanic with the exception of Dutch and Afrikaans.
Another way of putting this is as follows:
German in the widest sense including its origins and all its dialects that are not major national languages.
(I think it's clear that Dutch and Afrikaans are major national languages, but not Luxembourgish, which is only one of three official languages of a tiny country, and not Swiss German, which isn't an official language yet.) And yet another:
All continental West Germanic varieties on the German side of the German-Dutch subgroup. As a special exception for pragmatic reasons, also North and East Frisian.
I think these three quite different but equivalent definitions demonstrate that the scope that I am proposing is about as sharply defined as we can hope for. (Technically, some include East Frisian and some don't, but I wouldn't worry about that at all.)
PS: As has been pointed out below, questions presenting Yiddish text in Hebrew letters without transcription are problematic. I think a clarification similar to the following would make sense:
Questions related to Yiddish in the context of Judaism are usually asked over at Judaism SE. At the present site, Hebrew letters should always be accompanied by a Latin-based transcription.