[css-rhythm] Update introduction from JP industry meetup feedback

Author: kojiishi

css-rhythm/Overview.bs

@@ -83,11 +83,25 @@ This variant was very widely accepted in East Asia since the middle of '90s,
 such that most major word processors used in East Asia provided similar features
 by default.
 
+In East Asian publishing typography,
+the vertical rhythm is one of important properties,
+but its priority compared to other properties
+varies by types of documents.
+In single column documents,
+the priority is weaker than that of multi-column documents.
+Text should be on the vertical rhythm,
+but it is often preferred for borders, margins,
+or other properties to win over the rhythm.
+In such cases, the rhythm is shifted, similar to the casual variant.
+
 In this specification,
 when the 'line-height-step' property is used without combination of the 'block-step' property
 or the 'line-grid' property,
 it produces the similar effect as the East Asian casual vertical rhythm.
 
+It may also serve good for East Asian publishing typography,
+depends on the desired strength of the vertical rhythm.
+
 For other cases of vertical rhythm,
 it is expected that
 the 'block-step' property or the 'line-grid' property are used,
@@ -230,18 +244,18 @@ Notes on Block-level Boxes {#inline-block}
 Adjusting Block-level Box Heights {#block-height}
 =================================
 
-	Much web content includes blocks with varying font sizes, line heights, 
-	margins, etcetera. Adjusting line box heights may not be enough to 
-	achieve a vertical rhythm in these circumstances, 
-	and can negatively affect the readability of Latin scripts by altering line heights. 
-	Constraining block height, rather than line height, to a multiple of a step size 
+	Much web content includes blocks with varying font sizes, line heights,
+	margins, etcetera. Adjusting line box heights may not be enough to
+	achieve a vertical rhythm in these circumstances,
+	and can negatively affect the readability of Latin scripts by altering line heights.
+	Constraining block height, rather than line height, to a multiple of a step size
 	can achieve a vertical rhythm in these circumstances.
-	
+
 
 		<div class="figure">
 			<img src="images/block-step-size-before.png"
 			style="width: 500px">
-			<figcaption>Heads and blockquotes have varying font sizes and line heights, 
+			<figcaption>Heads and blockquotes have varying font sizes and line heights,
 			resulting in uneven text across columns.</figcaption>
 		</div>
 
@@ -250,7 +264,7 @@ Adjusting Block-level Box Heights {#block-height}
 		<div class="figure">
 			<img src="images/block-step-size-after.png"
 			style="width: 500px">
-			<figcaption>Space inserted before and after blocks (shown with colored borders) 
+			<figcaption>Space inserted before and after blocks (shown with colored borders)
 			restores vertical rhythm.</figcaption>
 		</div>