User blog comment:Rappy 4187/Technical Update: April 19, 2017/@comment-1611013-20170420171508/@comment-1824272-20170420174526

For chat popping out in a new window, that's always been the case for me for months. You can still force it to open in a new tab by right-clicking it and clicking "Open in new tab", or by middle-clicking it, like every other link on the internet.

As for not seeing all of the users in chat, Kirkburn said below that the feedback on that has been sent to their dev team.