Why does Translate highlight a space as an Illegal Character?
Unlike the Series 3 Shift-Space is considered an illegal character in OPL source. Shift-Space inserts a non-breaking space, regardless of the status of the caps lock, and looks identical to a normal space on screen. To make non-breaking spaces easier to identify tick the ‘Show spaces’ option in Tools Preferences… This shows spaces as dots and shifted spaces as ordinary spaces.