The Textarea could be improved with an autoselect on click a nowarp and an readonly attributes.
I also added wrapping comment marks.

This is my modified code in affiliates.module starting in line 1060:

...
    $output .= "<textarea rows=\"3\" cols=\"50\" onclick=\"this.select()\" wrap=\"off\" readonly=\"readonly\" style=\"font-size:10px;\";>";
    $output .= "&lt;!-- START BANNER " . strtoupper($row->label) . " --&gt;\n";

...

    $output .= "</a>";
    $output .= "\n&lt;!-- END BANNER " . strtoupper($row->label) . " --&gt;";
    $output .= "</textarea><br/>\n";
...

The rendered textarea would look like this:

<!-- START BANNER LABEL -->
<a href=".......
<!-- END BANNER LABEL -->

3 lines with an horizontal scrollbar, not editable and auto selecting the whole text when clicking into the textarea box wrapped with START/END comments