https://bugzilla.redhat.com/show_bug.cgi?id=857860
Werner Lemberg wl@gnu.org changed:
What |Removed |Added ---------------------------------------------------------------------------- CC| |wl@gnu.org
--- Comment #2 from Werner Lemberg wl@gnu.org --- This is not a bug. The calibri font contains some bitmap strokes for small sizes (among them for 15ppem, which is your 11pt at 96dpi). However, they are incomplete and cover only the latin1 glyph set. Ligatures like `fi' or `ti' are not covered. Additionally, the glyphs from the bitmap strokes are noticeably thinner.
If you want a consistent appearance, you have to disable bitmap strokes.