This feature allows authors to embed, in one document, content meant for specific individual users (e.g. allows a block of text to be visible only to a specified user who is a fully authorized internal user). When the activated document is rendered by a particular user, all content marked for other users is filtered out.
To mark content so that it is visible for only specific users, use span tags with a class attribute of "visible-only-to-user_qualified@domain".
For example, to embed content meant for user email@example.com only:
<span class="firstname.lastname@example.org"> Some info for John Smith's eyes only here.</span>
In the same document, to embed content meant for user email@example.com only:
<span class="firstname.lastname@example.org"> Some info for Jane Doe's eyes only here. </span>