Remove any reference to not existing forms in FormBuilderInterface::submitForm() documentation

It seems not. The topic in the last snippet shown in that page is "passing arguments that need to be passed by reference to the menu callback." This is the context.

Arguments that need to be passed by reference should not be included here, but rather placed directly in the $form_state build info array so that the reference can be preserved. For example, a form builder function with the following signature:

  function mymodule_form($form, &$form_state, &$object) {
  }

would be called via drupal_form_submit() as follows:

  $form_state['values'] = $my_form_values;
  $form_state['build_info']['args'] = array(&$object);
  drupal_form_submit('mymodule_form', $form_state);

Effectively, it seems a problem with how the part about the parameters is extracted from the comment.

/**
 * @param $form_id
 * …
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_form_submit(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called. Arguments that need to be passed by reference
 *   should not be included here, but rather placed directly in the $form_state
 *   build info array so that the reference can be preserved. For example, a
 *   form builder function with the following signature:
 *   @code
 *   function mymodule_form($form, &$form_state, &$object) {
 *   }
 *   @endcode
 *   would be called via drupal_form_submit() as follows:
 *   @code
 *   $form_state['values'] = $my_form_values;
 *   $form_state['build_info']['args'] = array(&$object);
 *   drupal_form_submit('mymodule_form', $form_state);
 *   @endcode
 * For example:
 * @code
 * // register a new user
 * $form_state = array();
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['mail'] = 'robouser@example.com';
 * $form_state['values']['pass']['pass1'] = 'password';
 * $form_state['values']['pass']['pass2'] = 'password';
 * $form_state['values']['op'] = t('Create new account');
 * drupal_form_submit('user_register_form', $form_state);
 * @endcode
 */

The "For example:" line is considered part of the @param block, while it is not. To resolve the issue, it should be enough to move the example code before the @param block.

This is a first tentative to resolve the issue.

As alternative, the example code is simply moved.

It's not a different example: It's the same example that is moved to solve an issue with the rendering.

The comment for that function is the following one.

/**
 * Retrieves, populates, and processes a form.
 *
 * This function allows you to supply values for form elements and submit a
 * form for processing. Compare to drupal_get_form(), which also builds and
 * processes a form, but does not allow you to supply values.
 *
 * There is no return value, but you can check to see if there are errors
 * by calling form_get_errors().
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms() and search_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most important is
 *   the $form_state['values'] collection, a tree of data used to simulate the
 *   incoming $_POST information from a user's form submission. If a key is not
 *   filled in $form_state['values'], then the default value of the respective
 *   element is used. To submit an unchecked checkbox or other control that
 *   browsers submit by not having a $_POST entry, include the key, but set the
 *   value to NULL.
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_form_submit(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called. Arguments that need to be passed by reference
 *   should not be included here, but rather placed directly in the $form_state
 *   build info array so that the reference can be preserved. For example, a
 *   form builder function with the following signature:
 *   @code
 *   function mymodule_form($form, &$form_state, &$object) {
 *   }
 *   @endcode
 *   would be called via drupal_form_submit() as follows:
 *   @code
 *   $form_state['values'] = $my_form_values;
 *   $form_state['build_info']['args'] = array(&$object);
 *   drupal_form_submit('mymodule_form', $form_state);
 *   @endcode
 * For example:
 * @code
 * // register a new user
 * $form_state = array();
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['mail'] = 'robouser@example.com';
 * $form_state['values']['pass']['pass1'] = 'password';
 * $form_state['values']['pass']['pass2'] = 'password';
 * $form_state['values']['op'] = t('Create new account');
 * drupal_form_submit('user_register_form', $form_state);
 * @endcode
 */

It is rendered as in the following screenshots.

Using "For example:" before the example doesn't seem to make sense, as that phrase would follow the following sentence:

There is no return value, but you can check to see if there are errors by calling form_get_errors().

drupal_static() uses just "Example:", before the examples.

Looking at the comment used for that function, this is what it contains.

/*
 * Example:
 * @code
 * function user_access($string, $account = NULL) {
 *   // Use the advanced drupal_static() pattern, since this is called very often.
 *   static $drupal_static_fast;
 *   if (!isset($drupal_static_fast)) {
 *     $drupal_static_fast['perm'] = &drupal_static(__FUNCTION__);
 *   }
 *   $perm = &$drupal_static_fast['perm'];
 *   ...
 * }
 * @endcode
 *
 * @param $name
 *   Globally unique name for the variable. For a function with only one static,
 *   variable, the function name (e.g. via the PHP magic __FUNCTION__ constant)
 *   is recommended. For a function with multiple static variables add a
 *   distinguishing suffix to the function name for each one.
 */

The examples are before the first @param directive.

The first example you are referring is about passing arguments that need to be passed by reference; it is not how the function is normally used, and I think it's worth pointing out how the function should be called in that case.
The second example is showing code that is not used in any of the functions calling drupal_form_submit() uses, and that code has a specific purpose.

Most of the Drupal functions are called from Drupal itself. IMO, that doesn't mean the documentation of a function should not evidence something that is relevant for calling the function. Differently, the documentation for drupal_static() should not report the advanced drupal_static() pattern, nor suggest using the PHP magic __FUNCTION__ constant, as that information can be obtained from Drupal code.

Drupal 8 doesn't have that function anymore, so I guess it doesn't have that documentation page either. Yet, Drupal 7 has that function, and the documentation page has that "bug."

I remove the reference to the node_edit form, since it doesn't exist a form with that ID, in Drupal 8. I also removed the example using the user registration form.