I think at leas one reason why the in-game chat is not used as much as it could/should be is that as soon as you take any action other than typing in chat, the window closes.
My main use for chat is during syndicate campaigns. If you are active in a campaign, then you will be doing many clicks (e.g. some opponents can take 25+ attacks to kill), so it is a pain to try and keep the chat window open during combat, and this is when it is the most useful, to provide coordination and communications with fellow syndicate members.
So my request is that If I open the chat window, that should be remembered between clicks and the window stay open until I close it. (even better might be an option to allow the user to specify the behaviour - stay open, or close after an action)