Hey Jules, the function keys are currently captured as characters in TextEditors and CodeEditorComponents. I think this is probably a bug.
In text editors they appear as a "u" with two dots on top, and in the CodeEditorComponent they show up as squares with an "x" in the middle. I've attached an image of the Introjucer. As a side note the CodeEditorComponent's caret is also misaligned with these characters.