In this sentence, the speaker is issuing Ian a command:
"Ian, set course for Mars Station."
This violates the rule about separating a noun from its verb with a comma. However, written:
"Ian set course for Mars Station."
it does not sound like a command to my ear, but like a statement of fact.
Is it incorrect to use a comma in this instance? If so, how can I prevent the sentence from reading like a statement rather than a command?