I have a dark GTK system theme (xfce4 dusk) which is inherited by all Qt applications. In QtCreator (with the default QtCreator theme), in the current version there are two widgets which seem to be forcing a black text color: The debug panel on the right showing global/stack variables, and the text output panel on the bottom, which prints special messages in their respective colors, but normal messages and stdout from the application in pitch black.

This is a regression because it didn't happen in an earlier version I used on Fedora 19, which was one of QtCreator 3.2.x.

Edit: Added a 4th screenshot showing the Open Documents panel, which uses the correct white text color from my theme.