Text rendering in Text or TextEdit shows square glyphs for some fonts under Ubuntu Trusty Tahr. Th attached test document shows that appears with Ubuntu and Arial fonts.
The document has been checked with OSX Mavericks, having Ubuntu font installed, and the issue does not appear there.
Text bug (I didn't check TextEdit) can be reproduced with several fonts (but not all) in QtQuick2 on Ubuntu 14.04 and Fedora 20. The bug is present with renderType both Text.QtRendering and Qt.NativeRendering. Can NOT be reproduced with QtWidgets or QtQuick1.