Karl,
What editor are you using? If you're on Textmate or E Text Editor (or
one of the other editors that support Textmate grammars), the syntax
highlighting should show up what is commented and what is not.
Example:
http://i.imgur.com/oIGj2.png
And with Chris's suggested fix:
http://imgur.com/CKa1D.png
If you have one of these editors and you're still having problems, you
may have an older copy of the Sass bundle which had problems,
particularly with comments. I've merged in some changes and done some
work lately to fix these problems:
http://github.com/charlesr/ruby-sass-tmbundle
Hope that helps.
Charles