I'm not sure if this is a libbatik problem or not:
When I generate monospaced output using the Creole ""monospace"" syntax, the SVG font-family attribute is output as "monospaced" which renders in a proportional font in Firefox Nightly on macOS Sierra. Editing the font-family to "monospace" (note the dropped "d" at the end) in the SVG file fixes the display.