For several years, the French Wikibooks displays the recent edits on the "deletion done" page to improve the admins work.
However, for a few weeks, we didn't touch anything but every time I delete a page, after the operation I get the following RC header with metacharacters (example from https://fr.wikibooks.org/w/index.php?title=Discussion_utilisateur:Adama_SINGUEPIRE&action=delete)