Comment 66 for bug 37828

You can just disable the ligatures in the fonts if you want, it's not hard. We disabled them in DejaVu for a long time because of this bug. But since there was no move towards fixing it we just enabled them again because we cannot cripple our fonts just because of one buggy program. If packagers want to do it, I'm not stopping them, but I'd rather see them patching a Firefox bug instead of removing features from our fonts.