Don't worry about that code - you only need to worry about the links to that code. Nobody that doesn't know how the thing works will bother trying unlinked sort methods. However, you can disable member status sorting by commenting out the 10 line, as well as the corresponding line in the public_directory template.
As for the links.. check out lines 90-92 of the public_directory template, which is the only place that users can toggle sorting by status...
... other than the dropdown menu on the splash page. That becomes a bit more interesting. You can probably get away with just commenting out or removing the block of HTML between lines 414 and 425.