Add issue for text-emphasis-style rendering

Author: kojiishi

css3-text/Overview.src.html

@@ -2884,6 +2884,10 @@ <h4 id="text-emphasis-style"><span class="secno">8.2.1</span>
       the glyph is missing in the font. The marks may instead be synthesized
       by the UA.</p>
 
+    <p class="issue">This rendering scheme is based on ruby algorithm and the one used in Japanese printing industries.
+      But the size of glyphs varies so much that this may reslut in inconsistent and/or bad visuals.
+      If you have any feedback on this, it's appreciated.</p>
+
     <p>The marks are drawn once for each grapheme cluster. However,
       emphasis marks are not drawn for a grapheme cluster consisting of:</p>
     <ul>