QGIS » QGIS Application

The Human Interface Guidelines include this:

2.Capitalise first letter only in labels:
Labels (and group box labels) should be written as a phrase with leading
capital letter, and all remaing words written with lower case first letters
I presume this rule is supposed to apply to labels in menus as well as everywhere else. But the majority of labels in menus (including context menus) in QGIS are in Title Case (at least when using English).

I guess if someone had the resources they could do a complete review of the UI vs the HIG. There are other obvious problems, such as sporadic implementation of this:
13.If clicking a button will spawn a new dialog, an ellipsis (...) should be
suffixed to the button text.