You have `Menu->Edit->Preferences->Editor->Display->Long Line Marker` enabled and set to `background` but the colour scheme yo are using has chosen a bad colour for the background.
Either disable the marker or set it to `Line` or fiddle with the colour scheme (personally I just use `Line` :) -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/geany/geany/issues/1645#issuecomment-336697613
