In #23104 (moved) we tried to make the line height uniform in order to avoid operating system fingerprinting. It seems that affects some systems in a way that lower parts of letters in the URL bar are eaten:
Text drifts slightly in the Browser Console. Is this because of this feature?
Could be if you are using 7.5a5. You could test whether disabling fingerprinting resistance fixes the issue for you (this feature, as many other fingerprinting related ones, is bound to privacy.resistFingerprinting which we set to true).
And just to make sure we are in the same page, when the JavaScript is disabled (noscript), the page content doesn't render properly. Even in Firefox Quantum.