I checked in the patch in bug 289480, and only Mac likes it. The Linux failure looks like bug 404698, but I don't know for sure. The Windows failure is possibly bug 405384. Anyway, opening this bug to track...
Created attachment 294157 [details] Diff between Linux test and reference I think this basically confirms the font hypothesis. This image and the previous one, by the way, were expertly drawn by the artist formerly known as luser.
10 years ago
Events overtook you - the Linux bits (at the time, which may or may not have been your Linux bits) got masked in bug 588271, the current Windows issue is D2D-only in bug 578114, and non-D2D in bug 579548, neither one of which seem to be what your Windows bits were. I'll fix the way the annotation still points here in bug 578114.