The comment editor does not include the necessary div to show editor related error messages

The page-editor.js makes use of a method called Confluence.Editor.addErrorMessage() which relies on the following structure being in the DOM -

<div id="editor-precursor">
    <div class="cell">
        <div id="content-title-div">
            ...snip...
        </div>

        <div id="editor-messages">
            ...snip...
        </div>
        <div id="all-messages">
            ...snip...
        </div>
    </div>
</div>

Neither the comment editor or the new quick-comment editor have this structure present and so any reported messages would be lost.

The only message currently being lost (disregarding anything external plugins might do) is an error on trying to preview content.