emphasis syntax has similar syntax, prevent conflicts

data/pages/wiki/syntax.txt

@@ -319,7 +319,7 @@ As you can see, it's the cell separator before a cell which decides about the fo
   ^ Heading 4    | no colspan this time |                    |
   ^ Heading 5    | Row 2 Col 2          | Row 2 Col 3        |
 
-You can have rowspans (vertically connected cells) by adding '':::'' into the cells below the one to which they should connect.
+You can have rowspans (vertically connected cells) by adding ''%%:::%%'' into the cells below the one to which they should connect.
 
 ^ Heading 1      ^ Heading 2                  ^ Heading 3          ^
 | Row 1 Col 1    | this cell spans vertically | Row 1 Col 3        |