You can't really put in broken code. Comments are in Yellow Blocks already and the comment is where the explanation goes...
Not as much a language/code IDE like visual studio... I can't think of a time where I have ever had an event that broke the game when it ran, so highlighting "bad" code in read doesn't make a lot of sense here. If you put something in a text box that you can't use it tells you and makes you correct it before it adds it to the event sheet.
I am not saying they are bad ideas, I just don't see them mapping as well to Construct as they do to Visual Studio...