I just edited my first answer on SO and got rejected. The user afterwards edited his answer himself - in roughly the same way. After asking why he didn't use my edit in the first place I got the following answer:
Because it wasn't appropriate for you to make that edit - adding more material rather than just honing the existing material - whereas it's fine for the original author to do that.
After reading https://stackoverflow.com/help/privileges/edit again, I still don't know why my edit hasn't been "appropriate". Can somebody help me out?