FYI… after upgrading to JetPack 3.3, I did have to make the manual edits above (as expected).
However, before making those changes, I “hovered” over a few Excerpts and noted a related issue: If an Ampersand… “&”… was used in the text of the Related Post, it displayed as “amps;” in the pop-up excerpt.
So for example, if in a Related Post, “Lakefront homes & sites” was used, it would display as “Lakefront homes amps; sites” in the hover/pop-up text.
HOWEVER, after using the edits you recommended (noted below), the Ampersand was displayed correctly.
*************************manual edits********************
I went into : jetpack/modules/related-posts/jetpack-related-posts.php
Then commented out the original code and added replacement:
/**JRN EDIT Change This:
‘excerpt’ => $this->_to_utf8( $this->_get_excerpt( $post->post_excerpt, $post->post_content ) ),
To This:
*/
‘excerpt’ => html_entity_decode($this->_to_utf8( $this->_get_excerpt( $post->post_excerpt,
$post->post_content ) ),ENT_QUOTES, ‘UTF-8’ ),