The problem is not that information has been added. The problem is that by merely occupying part of the limited screen space available for message previews, the text takes away useful information that was there before - specifically, a line of text from the body of the message.
I pre-filter Discourse messages into a dedicated maibox, so I already know why the messages got there. I now see this new text in the preview of every message in that mailbox instead of text that actually previews the message. It’s not useful to me, and displaces something that is.
It also seems that this text appears for the first message of a new topic. In that case it simply isn’t true - the message isn’t a reply to anything.
Martyn