Comment 5 for bug 348873

Note that this bug seems to manifest itself on all hinting settings except for 'Slight' (as set by the Gnome appearance configuration utility). This bug seems to affect other, proportional fonts as well, but the effect is much more profound in monospaced fonts.

I'm not sure it is related to bug 345189 at this time, as it's not the overall size of the font that changes, but the tracking (letter spacing).