Comment 6 for bug 697791

macslow: I remain unconvinced that the fix is as appropriate or simple as perceived; where's another screenshot taken with a much larger-sized font settings (32pt, still 96dpi). In this case the baseline has 12 pixels below and 14 pixels above the cap-height, which 4 pixels below the descenders and 11 above the ascenders.

It's far more likely that the error (in indeed this is any) is being introduced from hinting or rounding, and if so shifting it at the drawing stage with a heavy one-pixel hammer may not actually solve things across the board.