[css-fonts-3] fix issues noted on the call by @fantasai

Author: svgeesus

css-fonts-3/Fonts.src.html

@@ -3018,7 +3018,7 @@ <h3 id="font-variant-position-prop">Subscript and superscript forms: the <a href
 applied. This is done per run to avoid a mixture of variant glyphs and
 synthesized ones that would not align correctly. In the case of OpenType
 fonts that lack subscript or superscript glyphs for a given character,
-user agents <!-- must --> should synthesize appropriate subscript and superscript
+user agents <em>must</em> synthesize appropriate subscript and superscript
 glyphs.</p>
 
 <div class="figure"><img alt="alternate superscripts vs. glyphs synthesized using superscript metrics" src="superscript-alt-synth.png" /><p class="caption">Superscript alternate glyph (left), synthesized superscript glyphs (middle),  and incorrect mixture of the two (right)</p></div>
@@ -3029,7 +3029,7 @@ <h3 id="font-variant-position-prop">Subscript and superscript forms: the <a href
 -->
 <p>In situations where text decorations are only applied to runs
 of text containing superscript or subscript glyphs, the synthesized
-glyphs <!-- must --> should be used, to avoid problems with the placement of decorations.</p>
+glyphs may be used, to avoid problems with the placement of decorations.</p>
 
 <p>In the past, user agents have used font-size and
 vertical-align to simulate subscripts and superscripts for the