Recently I've discovered that if there are multiple values of the same parameter in postgresql.conf PostgreSQL will silently use the last one. It looks like not the best approach to me. For instance, user can find the first value in the config file and expect that it will be used, etc.
Postgres configuration file concept is based on overriding parameter values. It would be annoying if we emit warning for this feature. Also, it is easier to know which file/line the parameter value came from. You can check for duplicates with a small script.
