Articles titles displayed vertically in my WP control panel

Hi Stéphane. During my testing I encountered three problems. You kindly solved two of them (missing continue reading button and <p> tags not showing in the editor after switching between text and visual tabs). Now that’s the third one.

In my ignorance I think it’s a small problem compared to the others, but anyway… In my WP control panel, I see the titles of my articles displayed vertically, so it’s very difficult for me reading them. Conversely, pages titles don’t have this problem and are displayed properly. Is there any way to fix this? Thank you.