SO
Set Visual SO 'nnn | "char"
(Default=None)
If you edit text containing ShiftOut characters, they will not appear on the screen. From the location of ShiftOut, the display switches to the alternate character set which typically is the Line Drawing set. When you press Enter, the terminal or terminal emulator automatically inserts an escape sequence in front of the ShiftOut. The escape sequence is <esc>)B. To get around this problem, you can define another character as a translation for the ShiftOut character. For example, Set Vis SO "|" defines "|" to represent ShiftOut.
When Visual needs to print a ShiftOut on the screen, it prints a "|" instead. When Visual sees any "|" on the screen, it converts it into a ShiftOut internally. To avoid turning every occurrence of the "alias" character in your file into a ShiftOut, Visual prints a "?" for any line with a valid alias already in it and will not let you update that line in Visual mode (use Modify instead).