I appreciate a comma. My favorite kind is the one called into action by the vocative case. It's extraordinary that folks rarely use 'em these days. As in, "Not even you, dear." See? If we replace "dear" with someone's name, we still need the comma!
I hope this has been helpful to you. (Or remove "to" and replace with comma on the page, document and/or feed!) As in, "I hope this has been helpful, you."
This goes for all salutations that are directed toward a person as well.
I hope you have a great day, (insert name here)!
Or, finally, for the example from Nick Daws' blog:
"Don't marry Sean." He has BAD hair!
"Don't marry, Sean." No one understands you like I do.
11" x 8.5"
mixed media on index
AND last but not least:
Happy Birthday, Dad!
Happy Birthday, Grandpa!
Happy Birthday, Jasmine!