When you add text on the left side of a link (external, internal) in article core the content is not merge with the link. Bug 53210 asks to change this.
When you add text on the left side of a link (external, internal) in the reference assistant the content is merge with the link. Someone asks to change this on https://fr.wikipedia.org/w/index.php?title=Wikipédia:ÉditeurVisuel/Avis&oldid=102556548#Gestion_des_liens
A solution might be : On clicking a link, show 2 sliders (left/right of the current link) to handle easily what is In what is Out of the link