Having a lot of difficulty getting add_editor_style() to load into source code

Had difficulty until finding parent theme was calling add_editor_style()

The Twenty Fourteen should wrap this so it's possible dequeueing the call with remove_action, not editing the parent functions.php

Correct Answer: Put add_editor_style('editor-style.css'); in a function hooked to after_setup_theme action hook. Pass the name of file you want to use for editor CSS as the argument, or skip the argument if you want the name to be 'editor-style.css' as it's optional.

Wrong Answer: The optional parameter doesn't seem to be optional. This works for me:

add_editor_style('editor-style.css');

And yep, it's okay to call it directly in your theme's functions.php.

You shouldn't call add_editor_style() directly in your functions.php file. Instead, you should wait until the plugins and themes have been loaded:

add_action( 'after_setup_theme', 'add_editor_style' );

If you already have a function hooked to after_setup_theme, you can call add_editor_style() inside there instead.

You then need create a file called editor-style.css and place it in your theme direcrory. You must not place it in a subfolder; otherwise it will not be found. Try using this code in editor-style.css, just to see if it is working:

body#tinymce.wp-editor { 
    font-family: Arial, Helvetica, sans-serif; 
    margin:10px; 
}

body#tinymce.wp-editor a {
    color: #ffa500;
}

If the editor appears in a different font with orange links, then it works!

Contuary to what you are assuming, editor-style.css will not show up under the "Stylesheets" section of Chrome's developer tools. This is because the visual editor is loaded in an <iframe> element; essentially it is on another webpage that is embedded into the new post page. On this external page is where the editor-style.css stylesheet is loaded.

If you really want to check is editor-style.css is loaded, you can right-click on the visual editor body and choose Inspect Element from the context menu. Just above the line that is highlighted, you should see a <link> element pointing to your editor-style.css file.

You should also read the Codex page for add_editor_style().