VMS Help RUNOFF, file, Qualifiers, /UNDERLINE_CHARACTER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /UNDERLINE_CHARACTER[="character"]
       /NOUNDERLINE_CHARACTER

    Positional qualifier.

    Specifies the character to be used for the underline character.
    Defaults to an underscore (_).  You can specify the underline
    character as a single printable character (enclosed in
    quotation marks) or as a number preceded by a radix indicator
    (%D, %O, or %X)  to represent the ASCII value of a printable or
    nonprintable character. A specification of /NOUNDERLINE_CHARACTER
    overrides any .ENABLE UNDERLINING command in the DSR file.

    This qualifier is incompatible with the /SEPARATE_UNDERLINE
    qualifier.