I've seen it, back around 1999, possibly konqueror? Something that let you drag around toolbars and if you moved the address bar to the left/right side it would change the direction of writing.
Let's say that testing it briefly was enough. Editing tilted text works up to around 45 degrees, steeper than that is a strain.
Good luck reading anything in latin script with a one-character wide vertical search bar. This would works for Chinese (that’s the traditional writing orientation) but definitely not for most other languages.
Let's say that testing it briefly was enough. Editing tilted text works up to around 45 degrees, steeper than that is a strain.