The RTL styles for the administration interface specify fonts that can be less than ideal with some of the scripts that are written from right to left.
For e.g., while serif fonts look great on screen with latin scripts, their equivalents in Hebrew are rather hard to read in anything less than about 18 points; Arial on the Mac has only latin glyphs and is not available at all on most Linux distros; Verdana has no Hebrew glyphs at all, etc.
I submitted a patch in ticket #6365 that among other things switched the RTL styles to all sans-serif fonts, but it was ignored - I don't know if this was on purpose or not, so I opened this ticket to focus the discussion on the fonts issue instead of other RTL related issues.
I suggest switching all fonts in the RTL styles to generic "sans-serif" fonts instead of specifying fonts that may only work for a certain script or a certain platform. That way, the best fonts will always be used on each platform and for each script.
