I think this is a variant on a frequently rejected feature.
Giving more measures to exclude people from communication has always been seen as a giant downside for BM.
However, I completely agree with your assessment. I get discouraged myself when needing to select multiple contacts myself when replying to a message.
But then again, I thought the new message system which Delvin is working on, would give you an option to 'reply to list' on all cases. If not, that should definitely be a feature.
