[css-text-decor-3] More clarifications to alphabetic underline positioning

Author: fantasai

css-text-decor-3/Overview.html

@@ -983,12 +983,14 @@ <h3 id=line-position><span class=secno>2.7. </span> Determining the
 
    <dt><a href="#alphabetic"><i>alphabetic</i></a> underlines
 
-   <dd> Align the line decoration to an average of the ideal underlines of
-    the considered fragments, assigning any inline with non-initial ‘<code
-    class=property>vertical-align</code>’ the ideal position of its parent,
-    but keeping the line decoration below the lowest alphabetic baseline
-    considered. (A considered alphabetic baseline can be above the averaged
-    position if the dominant baseline is non-alphabetic.)
+   <dd> Calculate an average of the ideal underlining offsets (from their
+    respective alphabetic baselines) of the considered fragments, assigning
+    any inline with non-initial ‘<code
+    class=property>vertical-align</code>’ the ideal offset of its parent.
+    Align the line decoration to the lowest alphabetic baseline considered,
+    with that calculated offset. (Alphabetic baselines can differ between
+    ‘<code class=css>baseline</code>’-aligned boxes if the dominant
+    baseline is non-alphabetic.)
 
    <dt>non-alphabetic underlines (and <a
     href="#under"><i>under</i></a>-positioned overlines)

css-text-decor-3/Overview.src.html

@@ -648,10 +648,13 @@ <h3 id="line-position">
 
     <dt><i>alphabetic</i> underlines
     <dd>
-      Align the line decoration to an average of the ideal underlines of the considered fragments,
-      assigning any inline with non-initial 'vertical-align' the ideal position of its parent,
-      but keeping the line decoration below the lowest alphabetic baseline considered.
-      (A considered alphabetic baseline can be above the averaged position if the dominant baseline is non-alphabetic.)
+      Calculate an average of the ideal underlining offsets
+      (from their respective alphabetic baselines)
+      of the considered fragments,
+      assigning any inline with non-initial 'vertical-align' the ideal offset of its parent.
+      Align the line decoration to the lowest alphabetic baseline considered,
+      with that calculated offset.
+      (Alphabetic baselines can differ between ''baseline''-aligned boxes if the dominant baseline is non-alphabetic.)
 
     <dt>non-alphabetic underlines (and <i>under</i>-positioned overlines)
     <dd>