Recipient list in the original message in a conversation seems to change when adding more people in a reply. I.e.
1. Logged in as Martin, create a message to Trygve. Trygve receives the message:
2. Trygve replies to the message, adding Erlend to the recipient list. The recipient list in the original message now changes to include Erlend in the list (if you are logged in as Trygve you must refresh your web browser to see this):
3. Erlend is now under the impression that he has also received the first message, since he is in the recipient list.
Expected behaviour: Erlend should not see the original message. Recipient lists for past messages should not be altered.
I've also reported this as an issue in Canvas.