After using unset($form['author']); for comment module drupal returns errors As I would like to allow users print their names with comments I added a new field called comment_name. To not have 2 fileds with name I used the code to unset filed "name" from comment.module 

function user_add_node_form_comment_form_alter(&amp;$form, &amp;$form_state) {
unset($form['author']);
return $form;
}


But after adding a comment I receive an error message 

Notice: Undefined index: name in function comment_form_validate() (line 2127 in file D:\sites\theme\www\modules\comment\comment.module).
Notice: Undefined index: mail in function comment_form_validate() (line 2140 in file D:\sites\theme\www\modules\comment\comment.module).
Notice: Undefined index: homepage in function comment_form_validate() (line 2143 in file D:\sites\theme\www\modules\comment\comment.module).


I guess it because I unset a form that has to validate if user logged in or not but don't know how to solve it. 

P.S. Also I use the Ajax Comments Module
You should try this if you just want to hide the comment default name field !

function user_add_node_form_comment_form_alter(&amp;$form, &amp;$form_state) {
  $form['author']['name']['#access'] = FALSE;
}