Here is the implementation. In wiki.pm I added:

# =========================
sub fixedFontText
{
	 my( $theText ) = @_;
	 # preserve white space, so replace it by "  " patterns
	 $theText =~ s/\t/	/go;
	 $theText =~ s|((?:[\s]{2})+)([^\s])|'  ' x (length($1) / 2) . "$2"|eg;
	 return "$theText";
}

Then, in # Emphasizing of sub getRenderedVersion I changed the fixed font regex to:

# Emphasizing
  s/([\s])=([^\s].*?[^\s])=([\s\,\.\;\:\!\?])/$1 . fixedFontText($2) . $3/geo;

Commited to TWikiAlphaRelease, version 02 Dec 2000.

-- PeterThoeny - 25 Nov 2000