Created attachment 158862 [details] sample calc file - create a new document - merge cells B1:D1 - Insert text "Trips FRA ✈️ IST" (see attached doc) - toggle Italics via toolbar - only "IST" is toggles italics, remaining cell stays normal - see screenshots attached
Created attachment 158863 [details] version
Created attachment 158864 [details] screen 1
"Trips FRA " has italic format as direct format not as cell's format, as such, changing cell's format doesn't change it. Edit the cell and you can see it, select that text and the Italic-icon it's enable, now you can change it.