It would be really cool if archiving a post would remove it from the notification list others have. As far as I know archiving pretty much makes it done. But other users still have a notification for it.
Usecase: group message used for support; Archiving pretty much makes it “dealt with” and so there’s no point for other people from the group to look at it.
I don’t know how relevant this is anymore, if you are just tracking the group you get rolled up counts so it vanishes. If you are watching, you opted for pain.