When a member has had all Conversation/PM permissions away, if a member sends them a conversation, can they still read it? I just checked the admin CP for the user group permissions and there was no separate option for just being able to view conversations. (Basically, I have a member who isn't allowed to start or reply to conversations because of various misbehaviours, but another member needs to send them a private one asking they avoid joining in each other's topics).
Currently there is no way to prevent members from replying to unlocked conversations in their Inbox.
If you prevent a member from starting conversations, they can still receive them. The only time they will not see a new conversation that has been sent to them is when they are ignoring that particular member.
If you have a need for a ‘Reply to personal conversations’ or ‘Receive personal conversations’ user group permissions, then may I suggest you request them here: