Version: (using KDE 4.1.2) OS: Linux Installed from: Ubuntu Packages Fonts become smaller when using two displays instead of laptop's main display. I'm using X.Org X Server 1.5.2 and nvidia drivers version 177.80.
Probably the resolution between the laptop display and the two displays is different, so the font "looks like" smaller. for example, if your desktop fonts are 14px, on a laptop display (1280x800) they will looks bigger than the same font on a 1600x1200 display.
Actually I can confirm this, at the same resolution the fonts are bigger when I connect one of my displays. If I connect the other or both at once then the fonts are smaller. Might be something in Qt relating to DPI settings.