On Windows 8 a disabled QLineEdit is shown as enabled when the mouse is hovered over the line edit. This happens with for example the Windows default theme (some of the high contrast themes don’t show this).

The issue can be reproduced by having a disabled QLineEdit and hovering the mouse over it. You can also see this with Designer in ‘Form’ -> ‘Form Settings…’ the ‘Margin’ and ‘Spacing’ QLineEdit elements that are disabled.