Ich komm damit leider nicht klar. Ich habe folgenden Code eingefügt, dieser verändert zwar das Textfeld, nicht aber das Input-Feld...
PHP
$comments_args = array('comment_field' => '<div class="form-group"><label for="comment">' . _x( 'Comment', 'noun' ) . '</label><div class="input-group"><span class="input-group-addon"><i class="glyphicon glyphicon-comment"></i></span><textarea id="comment" name="comment" rows="5" cols="75" placeholder="" class="form-control contact" aria-required="true" ></textarea><span class="glyphicon form-control-feedback" aria-hidden="true"></span></div><div class="help-block with-errors"></div></div>',
'author' => '<div class="form-group"><label for="author">' . __( 'Name', 'domainreference' ) . '</label><div class="input-group"><span class="input-group-addon"><i class="fa fa-user"></i></span><input type="text" class="form-control contact" id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) .'" size="30"' . $aria_req . ' /><span class="glyphicon form-control-feedback" aria-hidden="true"></span></div><div class="help-block with-errors"></div></div>', );
comment_form($comments_args);