I couldn't find this already raised apart from for mobile browsers, and this is a separate problem affecting desktop browsers (at least Firefox and Chrome, on at least Fedora and MacOS).
As an example, see this answer. The initial one line code block can be ignored. The problem occurs with the two larger code blocks further down, which have been deliberately sized to require no horizontal scrolling. In Firefox 65.0.1 on Windows 10 this shows correctly. Other OS/browser combinations show horizontal scroll bars and cut off some characters to the right, requiring scrolling to see them:
- Firefox 65.0 on Fedora 28: 6 characters cut off
- Firefox 65.0.1 on MacOS Mojave 10.14.3: 3 characters cut off
- Chrome 71.0.3578.98 (Developer Build) on Fedora 28: 3 characters cut off
- Chrome 72.0.3626.109 (Official Build) on MacOS Mojave 10.14.3: 4 characters cut off
I'd expect the horizontal width in characters to be consistent across operating systems and browsers, particularly as not having to scroll horizontally is much preferred and many users make an effort to provide for this.