Emphasize the important part of the note.

Author: tabatkins

css-scroll-snap/Overview.bs

@@ -686,11 +686,13 @@ Snapping Boxes that Overflow the Scrollport</h4>
         </figure>
 
         Note: If the author had instead set mandatory snap positions
-        on the headings of each section
+        on the <em>headings</em> of each section
         (rather than the sections themselves),
         the contents of the first and fifth sections
         would be partially inaccessible to the user,
         as the heading snap area does not extend to cover the whole section.
+        This is why it's a bad idea to use mandatory snap positions
+        on elements that might be widely spaced apart.
     </div>
 
 
@@ -1048,4 +1050,4 @@ Changes {#changes}
 		<li>Renamed 'scroll-padding' to 'scroll-padding' and extended its uses.
 		<li>Removed renaming issues because nobody came up with a better alternative to ''scroll-snap-type: mandatory | proximity'' or ''scroll-snap-stop: normal''.
 		<li>Miscellaneous clarifications.
-	</ul>
+	</ul>