You need to note that declining a flag doesn't always mean you raised the wrong flag. Sometimes, it means the moderator who reviewed your flag doesn't agree with you and it doesn't necessarily represent all other moderators' view.
It's an obviously chatty comment that really doesn't say much.
Well, it depends on how you interpret the word chatty. According to the linked Merriam-Webster dictionary, it means
tending to talk a lot : fond of chatting
having an informal style that is similar to friendly speech
The comment you flagged doesn't seem to belong to either of them and I don't agree with your saying "that really doesn't say much." because
- @DavidZ posted a comment suggesting an edit.
- The OP responded to the comment and edited the answer.
- In response to the edit, @DavidZ basically said, "Your edited answer reads more clear and helpful to me than the answer before the edit, thanks."
I don't think it is too chatty. Of course, we are discouraged to say just "thanks" in the comment, but I don't see any problem with responding to an edit with "That certainly helps, thanks".
To me, too chatty will apply to comments that don't add anything meaningful to a post and sound like a discussion that has nothing to do with the post. Again, others might differ.