[css-text-4] Clarify issues on text-align: <string>.

Author: dbaron

css-text-4/Overview.bs

@@ -755,7 +755,10 @@ Character-based Alignment in a Table Column</h3>
 	but that (or a different behavior) needs to be specified,
 	to describe what happens
 	when different occurrences of the alignment character
-	are in different fonts.</p>
+	are in different fonts.
+	(Further, is that the intended behavior?  Probably the most
+	significant use case to consider is bold vs. non-bold text,
+	which only varies slightly in width.)</p>
 
 	<div class="example">
 
@@ -853,10 +856,14 @@ Character-based Alignment in a Table Column</h3>
 
 	<p class="issue">This behavior of aligning as though
 	the alignment character had been inserted at the end of
-	the contents of the cell, 
+	the contents of the cell,
 	combined with center-of-character alignment,
-	will produce gaps on the end-side of any replaced elements
-	that are alone on a line with &lt;string&gt; text-alignment.
+	will produce gaps on the end-side of lines
+	that are alone on a line with &lt;string&gt; text-alignment,
+	when none of the lines of the column has the alignment character,
+	or, more importantly, when some of the lines
+	do have the alignment character,
+	but the column is not laid out at its max-content width.
 	This is probably undesirable.</p>
 
 	<p class="issue">When the alignment character is inserted at