Standalone ID Macro not visible in the WYSIWYG editor

Steps to reproduce:

1. Edit a page using the WYSIWYG editor
2. Go on an empty line (e.g., pressing enter)
3. Click the "+" icon and select "Other Macros"
4. Search for "Id" and select the Id macro, click "Select"
5. Enter any id
6. Click "Submit"

Expected result:

A placeholder "macro:id" is displayed.

Actual result:

An empty box with a border is displayed, when putting the cursor in another element the box disappears and just an empty area is displayed.

The root cause seems to be that at least Firefox puts a <br> inside the <div>-element such that it doesn't have zero height and therefore CKEditor thinks the widget is visible.