Look at https://www.mediawiki.org/w/index.php?title=Topic:T6u6n0e244ak3wta&action=history
The editor placed a link to https://en.wikipedia.org/wiki/Milène_Guermont which resulted in a [[Local link]] with the URL showing as the label. You can see my fix to the link in the thread's history.
(Also, the editor probably needs an explanation of how to create the article at frwiki and/or why it can't be done.)
^ The above was typed in Flow-with-wikitext. The below is Flow-with-VisualEditor. I wonder whether the links will behave differently?
The link was to https://en.wikipedia.org/wiki/Milène_Guermont. I wonder if a link to http://en.wikipedia.org/wiki/WP:MED (which has no accents) would behave the same. Or perhaps the percent-encoding is important? https://en.wikipedia.org/wiki/Mil%C3%A8ne_Guermont They all show proper (enwiki) targets when I hover over them.