About [[MediaWiki:Flow-whatlinkshere-header/fr]]

Thanks for looking into context-appropriate translation. The numbers preceded by a dollar sign are so-called "parameters": they are replaced with variable content by the software. As the message documentation says (displayed next to the translation editor), this $1 gets replaced by an URL. The order has to stay like that because of the link markup, for instance

[https://translatewiki.net/wiki/User:MPlauche MPlauche]

becomes MPlauche