No Notification on PM for blocked user

If you block a user right after they send you a message but before you read the message (because you saw it from notifications, or because you just don't want to deal), there is no way to mark the message read without temporarily unblocking the user.
It feels like the system *should* mark all interactions with the user read so that I don't have to deal with the person driving me crazy (and risk further messages) just because the timing worked out perfectly wrong.