Update README.md

Author: BoPeng

README.md

@@ -23,36 +23,36 @@ A markdown kernel for Jupyter sounds like a stupid idea because Jupyter has
 native Markdown cells. The problem is that Jupyter markdown cells are
 rendered at the frontend and do not interact with Jupyter kernels.
 It is therefore difficult to pass variables from kernels to markdown cells
-to create dynamic output.
+to create dynamic output, as what RStudio/RMarkdown has been doing for a while
+(See ipython/ipython#2592, jupyter/help#41,and  jupyter/notebook#3463 for related discussions).
 
 This markdown kernel is a simple Jupyter kernel that parses and displays
-the cell content as markdown. So that you can type in markdown texts
+ cell content as markdown. Cells with markdown texts such as
 
 ```
 * This is *important*
 * This is not. 
 ```
 
-and it would be rendered as
+would produce output
 
 * This is *important*
 * This is not. 
 
-
 But wait, this is *still stupid* because you can do the same thing in
 Jupyter, only easier. What is the point of a markdown kernel by itself?
 
-The answer is that you can use this markdown kernel with [SoS
+The answer is that you can use this a markdown kernel with [SoS
 Notebook](http://vatlab.github.com/sos-docs). In SoS Notebook, you can
-create variables in SoS (Python) and pass them to cells of Markdown kernel
+create variables in SoS (Python) and pass them to cells of a Markdown kernel
 as
 
 ```
 %expand
 The result of the analysis is {result}
 ```
 
-or if you have `{ }` in your text, you can specify an alternative sigil
+or if you have multiple `{ }` in your text, you can specify an alternative sigil
 
 ```
 %expand ${ }
@@ -61,4 +61,4 @@ The result of the analysis is ${result}
 as shown in
 ![example](https://user-images.githubusercontent.com/9889312/37932344-e1c13e96-310d-11e8-963c-5fe26c6523d1.png)
 
-Note that SoS recognizes the `%expand` magic and highlights the intepolated texts.
+Note that SoS recognizes the [`%expand` magic](https://vatlab.github.io/sos-docs/doc/documentation/SoS_Magics.html#magic_expand) and highlights the intepolated expressions. SoS essentially treats the cell content as [Python f-strings](https://www.python.org/dev/peps/pep-0498/) (with configurable sigil) so almost arbitrary Python expressions could be used. In addition, instead of passing variables from subkernels to SoS and to a markdown cell, you can use a [`%render` magic](https://vatlab.github.io/sos-docs/doc/documentation/SoS_Magics.html#magic_render) to render output from any subkernels as markdown.