Markdown documentation: Add more detail in anchor generation note

Change-Id: Ifd76f87ac0d0beca22870460cefb23ddb2b08f09

Documentation/markdown.md

diff --git a/Documentation/markdown.md b/Documentation/markdown.md
index fdc3031..22ed389 100644
--- a/Documentation/markdown.md
+++ b/Documentation/markdown.md
@@ -401,9 +401,9 @@
 *Anchor generation*
 
 * letters and digits, after removing accents (á →  a)
-* spaces are replaced with -
-* other characters are replaced with _
-* runs of - and _ are collapsed
+* spaces are replaced with hyphens (`-`)
+* other characters are replaced with underscores (`_`)
+* runs of hyphens and underscores are collapsed
 ***
 
 If a document contains the same named subsection under different