I don't know if you've recently upgraded to 17.10 (Artful) but that's know to ship with a bad release of libfreetype (2.8.0) that has severe TrueType font hinting regression. You can read everything about the bug here: https://bugs.kde.org/show_bug.cgi?id=376630 https://bugs.kde.org/show_bug.cgi?id=378523 and the bug I reported at trolltech here: https://bugreports.qt.io/browse/QTBUG-63792 Some people prefer to downgrade libfreetype to last known good, I went the other way (upgraded to 2.8.1 and fixed kdeglobals and trolltech.conf files). Martin