From that thread...
"One solution would be to add a nofollow checkbox. This is actually very easy, given the javascript code. Just add this to edit-link-form.php, around line 113:"
Code:
<tr>
<th scope="row"> <?php _e('following') ?> </th>
<td>
<label for="follow">
<input class="valinp" type="checkbox" name="follow" value="nofollow" id="nofollow" <?php xfn_check('follow', 'nofollow'); ?> />
<?php _e('nofollow') ?></label>
</td>
</tr>
"Voila. Checkbox produces nofollow code."
"I used wordpad and hate to count the line number. However, I put these lines of code just before these lines and got it works.
<tr>
<th scope="row"><?php _e('identity') ?></th>"