File Display

[GillesDesautels]

When a file is displayed the pattern looks like

top left channel___________________
middle + _ _ _ _ _ _ _ _ _ _
zero line ___________________
middle - _ _ _ _ _ _ _ _ _ _
bottom & top ___________________
middle + _ _ _ _ _ _ _ _ _ _
zero line ___________________
missing middle line
bottom line ___________________

This missing line in the display, is-it a bug or feature. It looks to me like a bug but if it is a feature how do we use it.
Gilles Desautels