On Safari, The API call InsertHtml() converts the preceding and following whitespace into a nonbreaking space ( ).
This Issue http://dev.fckeditor.net/ticket/1509 was raised for IE6/7. And from the discussion,
Since the in Safari and Opera is added by the browser rather than by FCKeditor, and they have a good reason for doing so. I suggest we only fix the issue for IE, and just leave it as-is in Opera and Safari.