PLURAL keyword for languages without grammatical plural forms

I see the problem. It is pretty obvious from Plural/Comparison_of_plural_rules_in_various_databases where ja and ko have implicit default n != 1 rule in MW while explicit no forms rules in other sets.

Short term fix is to avoid plural in messages, in longer term I think this would be appropritately solved by supporting explicit number forms like {{PLURAL:$1|0=something special|usual text}}.

Correct me if I'm wrong but this is only an issue for messages with special n=0 cases (for which we usually use different messages altogether).

I can see the short term fix will work most of the case. Sometimes we'd have to choose translation a bit inconsistent to original, but the difference would be minor anyway.

I'm not sure how to check whether it's a 'n=0' case or not. If MediaWiki:badaccess-groups/ja is a non 'n=0' case, I confirm it's also affected.

Handling this centrally in https://bugzilla.wikimedia.org/show_bug.cgi?id=40251