Steps to reproduce: try any example with QTextEdit or QLineEdit.

Mac 10.12, 10.11, perhaps below.

For example, use textedit example from examples/widgets/richtext/textedit

1. Build the example;
2. Equip the Mac with microphone and test it;
3. Run any standard Mac application like TextEdit, Firefox, Safari, etc
and click some text area;
4. From the menu Edit select "Start Dictation". On 10.12 observe that the floating system with microphone rises and you can dictate.
5. Start textedit example and click at the text area;
6. From the menu Edit select "Start Dictation". No system window with microphone rises and you cannot dictate. It does not work either when using the default for dictation double command key pressed.

There is no workaround.

The issue heavily impacts people with dyslexia.