Comma separated lists should obey regional settings

This was discussed at a bugsmash group triage meeting in relation to 🐛 Free tagging vocabularies: Treatment of comma in Chinese and Unicode Active by padanski and myself. We agreed that it would be helpful to have a clear decision if this is something Drupal should do.

I will ask in #multilingual.

Crossposting with #582534:

Looking at core\misc\autocomplete.es6.js, if you go to autocompleteSplitValues you'll see a hardcoded ",", so I guess this is still an issue.
IMHO this is a bug. We should support those OOTB, or at least provide easy workarounds (e.g. settings) around it.

Crossposting as well.

@penyaskito, thanks for commenting. This was discussed in a bugsmash group triage meeting with Pandaski. catch and myself. catch noted that the replacement for JQuery UI autocomplete should be checked to see if it has the same problem. 📌 Provide a new library to replace jQuery UI autocomplete Needs work . I have updated the other issue.

I wonder if this should be a Meta and the other issue a child?

Not sure how that's related, AFAIK core\misc\autocomplete.es6.js is Drupal space, not jquery ui.

To support this, we would need to have a language level config IMHO for "List separator", which defaults to the comma we used so far. Sites could customize this then. We can also ship with specific translations for the separators in the standard language list if the listed Arabic comma is more common used on Arabic contexts in general.

On the other hand, is autocomplete the only component that deals with comma separated lists? The server side PHP support would also need to support whatever per language value is set then and be super aware of the language context then it is using :)