ZCS 8.0.2

I noticed the sender and receiver are blank if the view is Conversation and Bubbles are enabled. Might be an enumerator bug since the list is represented for the entire conversation, and may vary from message to message. In Message view the list is static.

They are visible if you double-click and open the conversation in a new window, however.

Obvious workarounds are disable Bubbles, or the Conversation view.