I think I have found a little display bug, which of course does not prevent from working !
The issue is as follows:
when using the command '\ifoot' of the scr2page package, then a vertical line besides the line numbers is displayed,
as if the '\ifoot' command was block command which can be 'folded'. (an example can be found in the screenshot)
I assume the vertical line (corresponding to a code folding possibility) to be triggered by the '\if' string of the '\ifoot' command.
Indeed, other screenshots for which the '\ifoot' command has been successively replaced by the '\ofoot' and '\cfoot' commands, do not show this vertical code folding line.