If you press space or actively enter into combat during a mission dialog you are presently reading or listening to the dialog gets sent away. This behaviour discourages team play (and generally is bad-for multiplayer/teaming in missions).
This is because whilst Player 1 may not have finished the dialog, Player 2 might have already finished and initiated the next big fight.
The Mission Dialogs worked really well before the changes in Season 3 (which I was too late to notice). I used to be able to fight and read at the same time (which was joyous). I also used to be able to fight and sell my excess in the replicator (which was also handy and is not not possible).
Since this was something added to the game I have to assume someone has asked for this feature so it can't just be yanked out and put down (where it belongs IMO). So what I suggest is this, make it an option, with the simple title "Fire to Cancel Mission Dialog". This way, anoyone who likes to miss part of the mission detail when playing in a team can leave it on.
Complete Reasons with Example:
I played the new mission today with a fleet mate, and it was a glorious experience (well done on another fantastic mission)!
However, when I came to the part where I was chatting with the Reman (all the voice overs where excellent) my team-mate was slightly ahead and started the fight when I was only half way through the second dialog. I had to fire to defend myself and at first, all seemed well since the person continued to talk as I fought (great). However, maybe I pressed space, or maybe I moved too much but something caused the dialog to disapear (and it wasn't me pressing the F key). I was most agreived, and if it wasn't for the fact that I would be playing the mission again on another character I would be spitting bricks for missing part of the core dialog.
So, please please, put the control of the mission dialogs back in the hands of the player. Don't take them away for any reason unless I hit escape or press F or click "continue".
Please listen to this plea, because I want to play this game with friends not on my own and things like this really make that not possible. Also,in all honesty, the only thing keeping me playing regularly is playing with my friends in game so anything which puts a crimp in that is really not good for me.