I tested a page (integrated browser) and got a spurious spelling error.
This originated in a commented out section which structurally is like:
<!-- <div id="DE52b56055-92fc-4e7a-9967-58bd3204e5d1" class="IdentifiedAsSpellingError"><h3>Processing</h3></div> -->
The spell checker identified each instance of that class-name inside the div as an error.



