When a colleague of mine, using Outlook as mailer, transfers a message (or a meeting invitation), I see the message coming from initial sender, not my colleague: I don’t know who transfered the information.
Similar, the list of recepients for the transfered message is wrong, only the initial one or nothing: I don’t know who else got the information.
On such a message if I reply, it goes not to my colleague but to initial sender.
Situation is the same in conversation mode and in list mode (almost when message was received in conversation mode, not tested if in list mode when it arrives).