Perhaps continued at phab:T154030
In Chechen language, when you mean "and", you must write "and" two times. Example: Chechnya а, Russia а.
MediaWiki:Math-search-relation-0/ce а, MediaWiki:Smw finallistconjunct/ce а.
As far as I can see the first one is no used in lists. SMW does not allow localisation of the comma at all.
For MediaWiki core there is And (" and") and Comma-separator (", ").