Highlighting error in the way that long strings are handled in the Inspector.
Of a long string, only the first line is shown in the editor. When I click on the first line, a blue highlight appears that seems to be highlighting the entire multiline text, even though only one line is visible (see attached image).

2) How can we reproduce it using the example you attached.
Open __Prospector_Scene_0. Press Play.
Select _MainCamera in the Hierarchy pane.
Open the disclosure triangle next to the "Xmlr" variable in the Deck (Script) Component. Click the box next to "Xml Text".

Reproduced on 4.2 and 4.3 and 4.3.0b4