There is a question that I would like to clarify with your help.
In some languages addresses to a person are always separated by commas.
Instead, I noticed that in English most people would write "Good evening, Mr. Smith", but "Hi John" or "Hello Peter".
Is there a general rule regulating this?
In my opinion it should be "Hi, John". Because there is a comma in a sentence like this: "By the way, Mary, how are you today?"
What are your opinions?
And if English is not your mother tongue, please write how it is in your language. (Although I noticed that Italians write "Ciao Massimo" and Poles "Cześć Marysio").