perhaps, though that might be harder to gauge, say a mod or assistant is out for the day, and the board goes to hell, and admin comes in an deletes 50 messages or whatever..
also, say a board has a mod and 4 assistants, how would their "non-deletions" be accounted for and/or distributed...?
not disagreeing with your idea, just think it would be less straightforward to attribute non-action than actions that get overturned.