link to the man manual pages

document user agent issue vs portage fetching
https://bugs.gentoo.org/327229

--- a/doc/sample.wgetrc
+++ b/doc/sample.wgetrc
@@ -5,7 +5,10 @@
 ## You can use this file to change the default behaviour of wget or to
 ## avoid having to type many many command-line options. This file does
 ## not contain a comprehensive list of commands -- look at the manual
-## to find out what you can put into this file.
+## to find out what you can put into this file. You can find this here:
+##   $ info wget.info 'Startup File'
+## Or online here:
+##   https://www.gnu.org/software/wget/manual/wget.html#Startup-File
 ##
 ## Wget initialization file can reside in /usr/local/etc/wgetrc
 ## (global, for all users) or $HOME/.wgetrc (for a single user).
@@ -14,6 +15,11 @@
 ## as well as change them, in most cases, as the values on the
 ## commented-out lines are the default values (e.g. "off").
 
+## You should not modify user_agent in the global config file.  Instead,
+## keep that in your ~/.wgetrc file.  If you really want to modify it
+## globally, make sure you set a custom FETCHCOMMAND in your package
+## manager because you will randomly break fetching with some servers.
+
 
 ##
 ## Global settings (useful for setting up in /usr/local/etc/wgetrc).