To confirm the other chap and add a little more detail, such messages can be in one of three important states: unread, read, and replied to. The phones report t

To confirm the other chap and add a little more detail, such messages can be in one of three important states: unread, read, and replied to. The phones report this. If it's unread, you don't know whether they've seen it or not; if it's read, you know they have, but they haven't yet chosen to reply. Pointedly, perhaps. Rather significant difference, choice of word very intentional. Unfortunately this is genuinely a case of dad being out of touch, not a stylistic disagreement :)