Just to comment that this happens to me & in my organization also. Cannot say for certain if it relates to New Teams, but I know it is a rather new bug (can't be a feature for sure) and it is very concerning. How the behavior is that I go to a certain chat, be it a group or individual person, and I start typing and press enter, and suddenly the message is in a completely different chat. I have for example written a personal message to a meeting chat where were 250 people. Thank god I noticed it in seconds. This happens for multiple people in our organization, and it is a security risk as someone might share sensitive information for example about redundancies to a wide audience. Only thing I can think of is that somehow when starting to write, Teams picks up the first letter, like H from Hi, and moves to the first chat that has a person or name starting with H. As much as I have tried I have been unable to structurally reproduce it, but it happened to me this morning again. As our laptops are centrally goverend and updated, end users have no way of reinstalling or updating Teams themselves.