Playing around with view / density, zoom, font size, I got back to almost normal (see very thin photo below):edit: plus I used the Mozilla 'light' theme, which helped a lot as it used a different font style.
Through a combination of stuff I managed to get it back to almost normal. This fixed the folders and list:View/densityView/fontMozilla 'Light' themeView/zoom fixed the readability of the message pane
