One can send chat messages when chat is set to "command only", but they won't be able to see them

The bug

One can send chat messages even when chat is set to "command only" in chat settings. They will be unable to see the message, but others are still able to see it; this is very confusing behavior.

If this change was performed because the "cannot send chat message" message (chat.cannotSend) is confusing, then perhaps that message should be changed; even still, the current behavior is more confusing than that.

To reproduce

1. Connect 2 accounts to the server.
2. In one account, make sure that chat settings is set to "commands only".
3. In the other, make sure it is set to "shown".
4. Say something from the player set to commands only.
5. Observe that no message is displayed on that player's side, but a message is displayed on the other's side.

Note

This issue first surfaced in 13w36a (the first snapshot for 1.7); it was fine in 1.6.4. Prior to 13w36a, the handler for the chat packet rejected non-command chat messages if the player's chat visibility was commands only; now it only rejects chat messages if the visibility is set to hidden.