Resolution: Out of scope
Gentoo Linux 64-bit, KDE 4.9.1, Qt 4.8.3. The graphics driver doesn't seem to affect this; the problem is there with the official NVidia driver, the AMD Catalyst driver, and the open source xf86-video-ati driver.
(I reported this problem on the KDE tracker: https://bugs.kde.org/show_bug.cgi?id=306943, but I was told to report it here instead.)
It seems that some applications (for example krunner and ksnapshot) display fonts in a somewhat broken manner. To demonstrate, I attached a screenshot of krunner's "System Activity" in krunner_process_list.png. Look at how "Shared Mem" is rendered, for example. And the same process list display, but through "System Monitor" is in ksysguard_process_list.png. Notice how "System Monitor" has correct font display. I found out that I can trigger the same bug in System Monitor if I launch it with:
ksysguard -graphicssystem native
Then it looks like in screenshot ksysguard_process_list_native.png. Look for example at how the word "Table" (in "Process Table") is rendered compared to the previous screenshot.
Another application that has the same problem is KSnapshot. And indeed, if I launch it manually with:
ksnapshot -graphicssystem raster
then the problem goes away.
In System Settings, in the Desktop Effects section's "Advanced" tab, I have "Raster" set as the "Qt graphics system". My Linux distro (Gentoo) also has this set in the environment:
It would seem that some KDE application ignore those settings.
Steps to Reproduce:
1. Press Alt+F2 (or whatever shortcut you've set to bring up krunner.)
2. Click the "System Activity" button.
Fonts look weird.
Fonts should look the same as everywhere else.