It does not have the protective plastic, it is not a reflection, in person the black line is perfectly visible just when turning on and also for a few seconds when the letters "fractal" appear.It’s in the plastic protective cover, not in your screen. Probably only shows up on a white background. Not a bug for sure.
So let's say it's normal? Does it happen with your unit?As far as I know these artefacts are normal when switching on an LCD. There are displays you can avoid it by taking care of the power on sequence of the display itself in terms of when LCD is powered in relation to CPU startup and when backlight is switched on ... On other displays you cant :-(