Currently the monospaced font setting in user preferences doesn't allow dashes. This prevents valid values (such as Inconsolata-dz) and the CSS generic font-family sans-serif (admittedly a bizarre choice for monospaced font, but some prefer proportional even when the monospaced makes sense).
Reproduction:
-Go to Personal or Global Display Preferences
-Enter 13px sans-serif as the Monospaced Font
-Click Save Changes
Anticipated results:
-Monospaced font is changed to sans-serif
Actual results:
-Error stating "Monospaced font value "13px sans-serif" is unsafe. You may only enter letters, numbers, spaces, commas, periods, forward slashes and double quotes."
Version:
phabricator 2201c65eb73fb99b8625bea45c273d262f2c289f (Tue, Aug 23)
arcanist 89e8b48523844cc3eff8b775f8fae49e85f8fc22 (Fri, Aug 19)
phutil 237549280f08feb8852857b1d109dfb0aba345f0 (Mon, Aug 22)