I saw a post: «Let's eat grandma! ... Let's eat, grandma! Use commas, save lives!» I'm surprised...Because I am no longer using comma before the subject since I even see teachers no using it. I used to use comma in this case since I began to study English (in my native language we use it similarly), but as a never saw anyone using it in that way, I thought I was wrong, then I stopped using this. So, the correct is to use a commas before the subject as in 'Hello, folks!' (and not as in 'Hello folks!'), right?