We touched this code a lot. But I think what's going on here is unrelated. As far as I can see the translation was broken. It was fixed just a few days before this ticket was created, see https://translatewiki.net/wiki/Special:Diff/10264596. I believe it took a while before the fixed translation made it to the wiki.

It looks like the English text was changed recently in a similar way: https://translatewiki.net/w/i.php?title=MediaWiki:Visualeditor-dialog-transclusion-no-template-description/en&diff=10255788&oldid=6709446

So I guess that the $1 parameter has been changed from the full page name (Template:Blah) to just the name without namespace (Blah), and $2 was introduced with the full page name. This will break the link in all of the translations, until a translator updates each one. That can take weeks or months in languages with less smaller communities, and should be avoided.

You can check that, although Swedish (sv) was fixed, about half of the languages haven't been updated yet, and still use the wrong parameter for the link: https://translatewiki.net/wiki/Special:Translations/MediaWiki:Visualeditor-dialog-transclusion-no-template-description (outdated translations are marked with red background)

@thiemowmde If possible, can you instead introduce a new parameter without changing existing ones, or introduce an entirely new message key and delete the old message? This would cause the text to display in English until translated, but at least the parameters will work as expected, and it's usually a lesser problem.

(Or, I guess the other approach could be to update all of the messages on Translatewiki, as in this case it can be done without understanding the language.)