Idea is to make it so we can use <div> without spacing issues.
If you use a <div> around a <sup>®</sup>, there is a bug which adds an additional space before the ®. It seems this is an email editor bug fix that needs taken care of. Support sent me to a document where the following code was shown other than that I added in a <sup>®</sup> to test my theory that it was a bug when a superscript is used within a div tag.
Below is code that is in Marketo documentation, in which I simply added a ® with <sup> tag and the email editor adds in a space.
<div class="mktEditable" id="exampleText" mktoname="Main Body Text">
Optionally add<sup>®</sup> default text for the editable text area.
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