When delivering a MassMessage, it is not possible to use a multilingual header [heading, title, topic, subject], per https://meta.wikimedia.org/wiki/Newsletters/Translation#Known_limitations
This frustrates communities who have translated a message into their own language, but are unable to help with the delivered heading, until it is posted everywhere.
Please help determine the best way to implement this. Thanks!
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Note: We can //partially// use switch, e.g.
> {{subst:#switch:{{subst:CONTENTLANG}}|fr=Test message|#default=Test message 2}}
which [[https://fr.wikipedia.org/w/index.php?title=Discussion_utilisateur:Quiddity_(WMF)/Brouillon&diff=137059391&oldid=136983745|creates this semi-successful diff]], but it has 2 problems:
* The edit summary is the raw code
* The subject is restricted to 240 characters, which limits how many languages can be included. E.g. a long title, or many languages, will break like this:
{F7913147}