Using all parameters simultaneously is only useful if you want to indicate the language the message is in. This might be useful to others who have no idea what all those funny symbols are about, and might be used by bots to add new language defaults to the template. Far, far into the future. Really, really, far.
In all other cases, you'll never need to specify more than four parameters.
Use the optional parameter lang/language to specify the default message's language. If not specified, the first unnamed parameter is used. If neither is specified, the default is English.
Use the optional parameter who to replace "This user". Examples: "This Wikipedian", "This Commonist", "I", your username, "This European".
Use the optional parameter pronoun to provide your favorite pronoun, usually one of "his", "her", "its", "my". If not provided, the second unnamed parameter is used. Defaults to no pronoun used.
If that's not enough for you, the optional parameters verb and restofmessage let you replace the entire message by a text of your own choice. Takes the pain out of translating template source text. ;)
