Sure! I did the following:
- Went into the archived box and returned one message. Checked the badge—still 2.
- Marked that message as unread (via the Defer action). Checked the badge—still 2.
- Opened the message, archived it. Checked the badge—still 2.
And to be clear, yes I did this on a moderator message, not on one of my personal ones.
PS: thanks for your attention on this front!