For reference, this is how the new preview text is surfacing in Outlook for iOS for me - it’s not just an inbox snippet; it becomes the first visible line associated with the message, which is what users are reacting to.
![Outlook for iOS Mail screenshot showing “Someone replied to your post.” appearing prominently above the message content, with FW/[PM] prefixes visible](https://global.discourse-cdn.com/meta/original/4X/f/8/b/f8bb7ec708ca69d7f2fbf8e2e9f9252f48fde0d6.jpeg)
This seems consistent with %{email_preview} being added recently: even if intended as hidden preheader text for HTML emails, in practice it’s highly visible to users (at least in some clients / delivery paths), which explains the sudden complaints.