Hi Jean,
Some responses follow.
By focusing on a single individual are you likely to miss other
potential contributors who might be lurking?
I don't think there's a general rule here. For instance, if a reviewer
has blocked your patch and forgotten to re-review your next submission,
it's helpful to get the attention of that particular person. I suppose
you could engage in back-channel communication here, but isn't that worse?
We directly address each other a lot in the body of our posts -- and I
think that's fine. It's the direct address in the subject line that I
find jarring.
I don't see a big difference between summoning someone in the subject
line and summoning them in the body of the message. But I appreciate
your feelings that the former is more jarring. I guess I feel the
opposite way. It is jarring to me if I am summoned in the body of a
message which I overlooked because the subject didn't catch my eye.