Editor steals keyboard input?

In EditorView I am opening a non modal form (ie. Show() rather than ShowDialog() because of message loop issues). There I have a Textbox to type in. I was surprised to see that I can't type special chars like non-breaking hyphen or space as well as several others into my form with the well-known keyboard shortcuts. Instead they land in the active target segment in the Studio Editor.

I tried all the funny events available (KeyDown, ProcessKeyPreview ... ), even took few exotic measures (GetAsyncKeyState ...) and only stopped short of installing a key hook, all to no avail.

So, my question is, can this behaviour be switched off temporarily, so that my form can receive those shortcuts? How?