Fix links/formatting in markdown.md

Something that was not noted in the other commit that touched this file
is that because this is markdown which renders to html I changed the
comments in the form of:

	<=== no thank you

to

	<!-- no thank you -->

This was not strictly necessary but and for non html it might not even
make sense except that it is still rendered to html and in most cases
(if not all) it is html. This was done for the rest of the file now too.

markdown.md

@@ -165,7 +165,7 @@ unquoted attribute values.
 For example, please do NOT use:
 
 ```
-    <br/>                                                     <=== no thank you
+    <br/>                                                     <!-- no thank you -->
 ```
 
 Instead use just:
@@ -177,7 +177,7 @@ Instead use just:
 And for example, please do NOT use:
 
 ```
-    <hr/>                                                     <=== no thank you
+    <hr/>                                                     <!-- no thank you -->
 ```
 
 Instead use just:
@@ -191,7 +191,7 @@ And for example, please do NOT use:
 ```
     <img src="1984-anonymous-tattoo.jpg"
      alt="image of a tattoo of the 1984 anonymous C code"
-     width=600 height=401 />                                  <=== no thank you
+     width=600 height=401 />                                  <!-- no thank you -->
 ```
 
 Instead use just:
@@ -214,7 +214,7 @@ a trailing `<br>`.
 Instead of:
 
 ```
-    In markdown,\                                             <=== no thank you
+    In markdown,\                                             <!-- no thank you -->
     do NOT use trailing\
     backslashes outside of\
     a code block
@@ -251,7 +251,7 @@ Please do **NOT** use the markdown embedded image element.
 Instead of using this markdown element to embed an image:
 
 ```
-    ![alt text](filename.png "Title")                         <=== no thank you
+    ![alt text](filename.png "Title")                         <!-- no thank you -->
 ```
 
 Use an `<img ..>` HTML element with `alt=`, `width=` and `length=`
@@ -266,7 +266,7 @@ attributes:
 For example, instead of:
 
 ```
-    ![1984-anonymous-tattoo.jpg](1984-anonymous-tattoo.jpg)   <=== no thank you
+    ![1984-anonymous-tattoo.jpg](1984-anonymous-tattoo.jpg)   <!-- no thank you -->
 ```
 
 use this HTML:
@@ -318,7 +318,7 @@ to incorrect URLs or file paths.
 Instead of:
 
 ```
-    [some text](https://example.com/foo_(bar))                <=== no thank you
+    [some text](https://example.com/foo_(bar))                <!-- no thank you -->
 ```
 
 Use:
@@ -330,7 +330,7 @@ Use:
 Instead of:
 
 ```
-    This thing, ([some text](some/path)), is NOT ideal.       <=== no thank you
+    This thing, ([some text](some/path)), is NOT ideal.       <!-- no thank you -->
 ```
 
 Use:
@@ -357,7 +357,7 @@ Instead of:
         return foo;
     }
 ```
-C compilers cannot be given a -Wno-main-arg-errors flag.      <=== no thank you
+C compilers cannot be given a -Wno-main-arg-errors flag.      <!-- no thank you -->
 ````
 
 Use:
@@ -384,7 +384,7 @@ Please do **NOT** use parenthesis inside the markdown link titles.
 Instead of:
 
 ```
-    [some (text)](https://example.com/cyrds)                  <=== no thank you
+    [some (text)](https://example.com/cyrds)                  <!-- no thank you -->
 ```
 
 Use:
@@ -396,7 +396,7 @@ Use:
 Instead of:
 
 ```
-    [ls(1)](https://example.com/ls-man-page.1)                <=== no thank you
+    [ls(1)](https://example.com/ls-man-page.1)                <-- no thank you -->
 ```
 
 Use: