Add note about whitespace before comments. Related to #276

supervisor/skel/sample.conf

@@ -3,8 +3,10 @@
 ; For more information on the config file, please see:
 ; http://supervisord.org/configuration.html
 ;
-; Note: shell expansion ("~" or "$HOME") is not supported.  Environment
-; variables can be expanded using this syntax: "%(ENV_HOME)s".
+; Notes:
+;  - Shell expansion ("~" or "$HOME") is not supported.  Environment
+;    variables can be expanded using this syntax: "%(ENV_HOME)s".
+;  - Comments must have a leading space: "a=b ;comment" not "a=b;comment".
 
 [unix_http_server]
 file=/tmp/supervisor.sock   ; (the path to the socket file)