Well, for me, more than clarity, it's about following grammar rules. Hence, I want to clear this doubt.
A comma is used to keep separate ideas in a sentence separate. A good example of this is: I know Sarah…: Sarah and I are acquainted I know, Sarah,…: I know something ALWAYS use a comma with such ( except with appositives:) ...appointed to Acme Industries. John Smith, CEO stated… CEO John Smith stated...
Claire, I am acquainted with those rules — I just want to clarify my everyone (vocative case) doubt. I think you hinted at using a comma in that situation — if I am not mistaken.