Apparently it's considered a bug that someSome browsers have different default textarea fonts than others, so we certainly shouldn't be surfacing this behaviour as an option to users to actually use. And because OOjs UI is special and flat-out disallows this, using this user preference option with OOjs UI forms leads to inconsistency between editing interfaces in which the option just plain doesn't do what it says (always monospace regardless of what the browser default actually is)so there currently is an option for users to simply use whatever that is in lieu of anything specific.
Note: 'browser default'This causes problems for things which normalise fonts or define their own font stacks (such as OOjs UI and various skins), as it becomes no longer possible to maintain consistent fonts throughout the interface when one random part is explicitly not using the usual fonts. If users want a particular font (such as whatever is equivalent to their usual browser), they should just set their preference to that in general (if they want sans serif, they should just set it to that).
The current options become these classes:
Note: default is not just //an// option, but currently the default setting for the 'editfont' preference.