MediaWiki messages should allow the soft hyphen (HTML ­) in interface messages.
I first noticed this when I saw the message [[MediaWiki:Userrights/nb]], saying "Brukerrettighetskontroll", wrapped before "ll", like this: "Brukerrettighetskontro<br />ll". To fix this I wanted to insert soft hyphens so that if it wraps, it will wrap at the word boundaries, like this: "Bruker­rettighets­kontroll", but when I did this the ­ was converted to &shy;.
Some examples of how it looks in various variants can be seen here: https://no.wikipedia.org/w/index.php?title=Wikipedia:Sandkasse&oldid=15777471
See also T66528.