I've run into an issue where a member is complaining about a full inbox, yet claims it's only 37% full. It would help immensely to be able to view the member's profile in AdminCP and determine the number of messages that are in the person's inbox. Even if it's a separate function in AdminCP, there are times when we do need to see if an inbox is truly full, or if there's another issue that needs to be investigated.
Correct. It would still be a good thing to be able to determine the number of messages that are in someone's inbox. Don't want to read 'em. Just want to know who the packrats are when they start complaining.
This would probably be better requested from the add-on developer rather than in the core because, as already stared, there's no conversation limit in XenForo, therefore there's no real need to know how many conversations a user has.