Launch https://fr.wikipedia.org/w/index.php?title=Tintin_au_pays_des_Soviets&oldid=147961827&veaction=edit in the visual editor, hover over the first sentence. Notice it gets "caught" by Infobox Bande dessinée, and can't be edited normally. You have to click on it, which opens the complex transclusion editor, and scroll all the way to the end of that dialog box to find the first sentence in its "Content" field.
Adding an empty line after the infobox looks like a workaround. Is using a bot to apply it the only thing to do here?