Kathleen’s question: “Recently, I have noticed replies to me with ‘Thanks, Kathleen.’ The comma annoys me and just looks and sounds wrong. Is this the correct way of writing this?”
BizWritingTip response: Grammatically, Thanks, Kathleen means Kathleen is thanking someone else.
Thanks, Kathleen is a shortened version of
On the other hand, Thanks Kathleen (no comma) means Kathleen is being thanked by the sender of the message.
Note: I suspect this grammar rule will change over time because of technology. When you are trying to squeeze a message onto a small space, it makes sense to place Thanks, Kathleen on the same line.
However, because finding the comma can take more time on screen keyboards, I think senders will stop using it. Frankly, I don’t think it will cause any confusion.