Actually I can reproduce it :
- Go to linux@lemmy.ml
- Check posts "Progress Report: Linux 7.2 - Asahi Linux" are unread, 2 exists on the same community :
- Open one, go back : both are marked read in the list of posts even though mark duplicates as read is off (also checked view current settings)
- If you were also subscribed to linux@programming.dev then open it : same post is also read even though you didn't open it