Clarify optional credentials and required topic values

README.md

@@ -101,9 +101,9 @@ different, and cannot contain `+` or `#` wildcards. There is no hidden prefix
 or fallback to the original installation's topics. Set a unique `client_id`
 if several controllers share a broker.
 
-Enter values without surrounding quotes.
-Leave both blank only if anonymous access is permitted. Values are literal;
-`%` and `#` within values are supported. Credentials are not passed as CLI
+Leave username/password blank only if anonymous access is permitted.
+Credential values are literal; `%` and `#` within passwords are supported.
+Credentials are not passed as CLI
 arguments and are not included in this repository.
 
 The private INI is created with permissions `0600` and is excluded from Git.