In some circumstances, the label and the value in OO.ui.TextInputWidget overlap when the label is aligned to the left. There's a screenshot below, and sample code on testwiki.

The widget returns to normal when it is focused. Also, the overlapping doesn't occur if the text input widget is added directly to the page, or if the window is opened on page load rather than via a portlet link. Presumably in these cases some DOM event is causing the widget to be updated in the same manner as when it is focused.

I'm seeing the overlapping in both Firefox and Chrome on Ubuntu.